fix: make the app keyboard-reachable, and close four DoS-able patterns

The bulk of what SonarQube still had open on the reliability side, read site by
site rather than swept. Two clusters are worth calling out because they are
defects, not lint.

**Four regexes could be made to hang the process.** The worst is
`/.+@.+\..+/` in the forgot-password path: three unbounded `.+` that all
overlap, unanchored, on an endpoint that needs no login and whose schema is a
bare z.string() under a 100kb body cap. A thousand '@' characters had not
finished after 100 seconds — one request pins the event loop, and Node has one.
EMAIL_REGEX in auth.helpers is the same shape on register and profile update
(310ms for 8kb). The two tag strippers over an uploaded KML description and over
Commons metadata took 0.52s on a 16k run of '<'. Each rewrite was proven
equivalent by brute force against the original — millions of strings for the
coordinate patterns, 671,876 for the tag stripper — because a subtly different
regex on a parsing path is worse than the finding.

`<[^>]+>` could not be fixed in the pattern: `[^>]` matches `<` too, so the only
unambiguous form changes what happens to malformed markup. It is now a scan in
common/stripHtmlTags.ts, quirks included — `<>` is left alone, `<a<b>` is one
tag — with the equivalence pinned by a test that compares against the old regex
over every string up to length six.

**And roughly 500 places could only be reached with a mouse.** Clickable divs
became real buttons where the markup allowed (52 of them), took
role + tabIndex + Enter/Space where they had to stay divs, and modal backdrops
took role="presentation" — the honest role, since a backdrop is a mouse shortcut
for a Cancel control that is already in the tab order, and making it a button
plants a nameless full-screen tab stop around its own contents.

Alongside those: `.sort()` calls that now say the order they always had, `{n &&
<X/>}` guards that rendered a literal "0" for a zero-byte file and for a place at
latitude 0, an optimistic budget write that stored a boolean where the contract
and both transports use 0/1, and the Number statics.

sonar-project.properties documents the six that were deliberately left: two wiki
patterns with no overlapping quantifier pair whose "fix" would stop parsing
`[see [1]](url)`, four tar header fields bounded at 12-155 bytes by the format,
two djb2 hashes where the 32-bit wrap is the algorithm, two `| 0` that are also
coercing undefined to 0 on a path where the API sends no user_id, and the MCP
session maps Sonar reads as empty because they are filled from another module.

client/src/components/Files/FileManagerAssignModal.tsx

@@ -9,9 +9,9 @@ import { transportIcon } from './FileManager.helpers'
 export function AssignModal(S: FileManagerState) {
   const { files, assignFileId, setAssignFileId, t, days, assignments, places, reservations, tripId, handleAssign, refreshFiles } = S
   return createPortal(
-    <div style={{ position: 'fixed', inset: 0, background: 'rgba(0,0,0,0.5)', zIndex: 5000, display: 'flex', alignItems: 'center', justifyContent: 'center' }}
+    <div role="presentation" style={{ position: 'fixed', inset: 0, background: 'rgba(0,0,0,0.5)', zIndex: 5000, display: 'flex', alignItems: 'center', justifyContent: 'center' }}
       onClick={() => setAssignFileId(null)}>
-      <div style={{
+      <div role="presentation" style={{
         background: 'var(--bg-card)', borderRadius: 16, boxShadow: '0 20px 60px rgba(0,0,0,0.2)',
         width: 'min(600px, calc(100vw - 32px))', maxHeight: '70vh', overflow: 'hidden', display: 'flex', flexDirection: 'column',
       }} onClick={e => e.stopPropagation()}>

client/src/components/Files/FileManagerAvatarChip.tsx

@@ -24,7 +24,7 @@ export function AvatarChip({ name, avatarUrl, size = 20 }: { name: string; avata
           cursor: 'default',
         }}>
         {avatarUrl
-          ? <img src={avatarUrl} style={{ width: '100%', height: '100%', objectFit: 'cover' }} />
+          ? <img src={avatarUrl} alt={name} style={{ width: '100%', height: '100%', objectFit: 'cover' }} />
           : name?.[0]?.toUpperCase()
         }
       </div>

client/src/components/Files/FileManagerImageLightbox.tsx

@@ -68,8 +68,12 @@ export function ImageLightbox({ files, initialIndex, onClose }: ImageLightboxPro
 
   return (
     <div
+      // Backdrop only — Escape and the header's close button do the same job for
+      // the keyboard. Closing on the backdrop's own clicks (rather than letting
+      // every child stop the bubble) keeps the chrome free of click handlers.
+      role="presentation"
       style={{ position: 'fixed', inset: 0, background: 'rgba(0,0,0,0.92)', zIndex: 2000, display: 'flex', flexDirection: 'column', paddingBottom: 'var(--bottom-nav-h)' }}
-      onClick={onClose}
+      onClick={e => { if (e.target === e.currentTarget) onClose() }}
       onTouchStart={e => setTouchStart(e.touches[0].clientX)}
       onTouchEnd={e => {
         if (touchStart === null) return
@@ -80,7 +84,7 @@ export function ImageLightbox({ files, initialIndex, onClose }: ImageLightboxPro
       }}
     >
       {/* Header */}
-      <div style={{ display: 'flex', alignItems: 'center', justifyContent: 'space-between', padding: '10px 16px', flexShrink: 0 }} onClick={e => e.stopPropagation()}>
+      <div style={{ display: 'flex', alignItems: 'center', justifyContent: 'space-between', padding: '10px 16px', flexShrink: 0 }}>
         <span style={{ fontSize: 'calc(12px * var(--fs-scale-body, 1))', color: 'rgba(255,255,255,0.7)', overflow: 'hidden', textOverflow: 'ellipsis', whiteSpace: 'nowrap', flex: 1 }}>
           {file.original_name}
           <span style={{ marginLeft: 8, color: 'rgba(255,255,255,0.4)' }}>{index + 1} / {files.length}</span>
@@ -105,22 +109,22 @@ export function ImageLightbox({ files, initialIndex, onClose }: ImageLightboxPro
       </div>
 
       {/* Main image + nav */}
-      <div style={{ flex: 1, display: 'flex', alignItems: 'center', justifyContent: 'center', position: 'relative', minHeight: 0 }}
+      <div role="presentation" style={{ flex: 1, display: 'flex', alignItems: 'center', justifyContent: 'center', position: 'relative', minHeight: 0 }}
         onClick={e => { if (e.target === e.currentTarget) onClose() }}>
         {navBtn('left', goPrev, hasPrev)}
         {fileIsVideo ? (
-          <div onClick={e => e.stopPropagation()}>
+          <div>
             <VideoPlayer src={file.url} style={{ maxWidth: '85vw', maxHeight: '80vh', borderRadius: 8 }} />
           </div>
         ) : (
-          imgSrc && <img src={imgSrc} alt={file.original_name} style={{ maxWidth: '85vw', maxHeight: '80vh', objectFit: 'contain', borderRadius: 8, display: 'block' }} onClick={e => e.stopPropagation()} />
+          imgSrc && <img src={imgSrc} alt={file.original_name} style={{ maxWidth: '85vw', maxHeight: '80vh', objectFit: 'contain', borderRadius: 8, display: 'block' }} />
         )}
         {navBtn('right', goNext, hasNext)}
       </div>
 
       {/* Thumbnail strip */}
       {files.length > 1 && (
-        <div style={{ display: 'flex', gap: 4, justifyContent: 'center', padding: '10px 16px', flexShrink: 0, overflowX: 'auto' }} onClick={e => e.stopPropagation()}>
+        <div style={{ display: 'flex', gap: 4, justifyContent: 'center', padding: '10px 16px', flexShrink: 0, overflowX: 'auto' }}>
           {files.map((f, i) => (
             <ThumbImg key={f.id} file={f} active={i === index} onClick={() => setIndex(i)} />
           ))}

client/src/components/Files/FileManagerMarkdownPreviewModal.tsx

@@ -34,10 +34,12 @@ export function MarkdownPreviewModal(S: FileManagerState) {
 
   return createPortal(
     <div
+      role="presentation"
       style={{ position: 'fixed', inset: 0, background: 'rgba(0,0,0,0.85)', zIndex: 10000, display: 'flex', alignItems: 'center', justifyContent: 'center', padding: 16 }}
       onClick={() => setPreviewFile(null)}
     >
       <div
+        role="presentation"
         style={{ width: '100%', maxWidth: 820, height: '94vh', background: 'var(--bg-card)', borderRadius: 12, overflow: 'hidden', display: 'flex', flexDirection: 'column', boxShadow: '0 20px 60px rgba(0,0,0,0.3)' }}
         onClick={e => e.stopPropagation()}
       >

client/src/components/Files/FileManagerPdfPreviewModal.tsx

@@ -8,10 +8,12 @@ export function PdfPreviewModal(S: FileManagerState) {
   const { previewFile, setPreviewFile, previewFileUrl, toast, t } = S
   return createPortal(
     <div
+      role="presentation"
       style={{ position: 'fixed', inset: 0, background: 'rgba(0,0,0,0.85)', zIndex: 10000, display: 'flex', alignItems: 'center', justifyContent: 'center', padding: 16 }}
       onClick={() => setPreviewFile(null)}
     >
       <div
+        role="presentation"
         style={{ width: '100%', maxWidth: 950, height: '94vh', background: 'var(--bg-card)', borderRadius: 12, overflow: 'hidden', display: 'flex', flexDirection: 'column', boxShadow: '0 20px 60px rgba(0,0,0,0.3)' }}
         onClick={e => e.stopPropagation()}
       >

client/src/components/Files/FileManagerRow.tsx

@@ -34,10 +34,13 @@ export function FileRow(p: FileManagerState & { file: TripFile; isTrash?: boolea
       className="group"
     >
       {/* Icon or thumbnail */}
-      <div
+      <button
+        type="button"
+        disabled={isTrash}
+        aria-label={file.original_name}
         onClick={() => !isTrash && openFile(file)}
         style={{
-          flexShrink: 0, width: 36, height: 36, borderRadius: 8,
+          flexShrink: 0, width: 36, height: 36, borderRadius: 8, padding: 0,
           background: 'var(--bg-tertiary)', display: 'flex', alignItems: 'center', justifyContent: 'center',
           cursor: isTrash ? 'default' : 'pointer', overflow: 'hidden',
         }}
@@ -48,13 +51,13 @@ export function FileRow(p: FileManagerState & { file: TripFile; isTrash?: boolea
               const ext = (file.original_name || '').split('.').pop()?.toUpperCase() || '?'
               const isPdf = file.mime_type === 'application/pdf'
               return (
-                <div style={{ display: 'flex', flexDirection: 'column', alignItems: 'center', justifyContent: 'center', width: '100%', height: '100%', background: isPdf ? '#ef44441a' : 'var(--bg-tertiary)' }}>
+                <span style={{ display: 'flex', flexDirection: 'column', alignItems: 'center', justifyContent: 'center', width: '100%', height: '100%', background: isPdf ? '#ef44441a' : 'var(--bg-tertiary)' }}>
                   <span style={{ fontSize: 'calc(9px * var(--fs-scale-caption, 1))', fontWeight: 700, color: isPdf ? '#ef4444' : 'var(--text-muted)', letterSpacing: 0.3 }}>{ext}</span>
-                </div>
+                </span>
               )
             })()
         }
-      </div>
+      </button>
 
       {/* Info */}
       <div style={{ flex: 1, minWidth: 0 }}>
@@ -63,12 +66,14 @@ export function FileRow(p: FileManagerState & { file: TripFile; isTrash?: boolea
             <AvatarChip name={file.uploaded_by_name} avatarUrl={file.uploaded_by_avatar} size={20} />
           )}
           {!isTrash && file.starred ? <Star size={12} fill="#facc15" color="#facc15" style={{ flexShrink: 0 }} /> : null}
-          <span
+          <button
+            type="button"
+            disabled={isTrash}
             onClick={() => !isTrash && openFile(file)}
-            style={{ fontWeight: 500, fontSize: 'calc(13px * var(--fs-scale-body, 1))', color: 'var(--text-primary)', overflow: 'hidden', textOverflow: 'ellipsis', whiteSpace: 'nowrap', cursor: isTrash ? 'default' : 'pointer' }}
+            style={{ fontWeight: 500, fontSize: 'calc(13px * var(--fs-scale-body, 1))', color: 'var(--text-primary)', overflow: 'hidden', textOverflow: 'ellipsis', whiteSpace: 'nowrap', cursor: isTrash ? 'default' : 'pointer', textAlign: 'left', minWidth: 0 }}
           >
             {file.original_name}
-          </span>
+          </button>
         </div>
 
         {file.description && (
@@ -76,7 +81,7 @@ export function FileRow(p: FileManagerState & { file: TripFile; isTrash?: boolea
         )}
 
         <div style={{ display: 'flex', alignItems: 'center', flexWrap: 'wrap', gap: 6, marginTop: 4 }}>
-          {file.file_size && <span style={{ fontSize: 'calc(11px * var(--fs-scale-caption, 1))', color: 'var(--text-faint)' }}>{formatSize(file.file_size)}</span>}
+          {!!file.file_size && <span style={{ fontSize: 'calc(11px * var(--fs-scale-caption, 1))', color: 'var(--text-faint)' }}>{formatSize(file.file_size)}</span>}
           <span style={{ fontSize: 'calc(11px * var(--fs-scale-caption, 1))', color: 'var(--text-faint)' }}>{formatDateWithLocale(file.created_at, locale)}</span>
 
           {linkedPlaces.map(p => (
@@ -87,7 +92,7 @@ export function FileRow(p: FileManagerState & { file: TripFile; isTrash?: boolea
               ? <SourceBadge key={r.id} icon={transportIcon(r.type)} label={`${t('files.sourceTransport')} · ${r.title || t('files.sourceTransport')}`} />
               : <SourceBadge key={r.id} icon={Ticket} label={`${t('files.sourceBooking')} · ${r.title || t('files.sourceBooking')}`} />
           ))}
-          {file.note_id && (
+          {!!file.note_id && (
             <SourceBadge icon={StickyNote} label={t('files.sourceCollab') || 'Collab Notes'} />
           )}
         </div>