fix(collab): preserve line breaks in notes display (#608)

Add remark-breaks plugin so single newlines in note content render
as <br> instead of being collapsed by Markdown. Applies to both
the card preview and the expanded view.

client/src/components/Collab/CollabNotes.tsx

@@ -3,6 +3,7 @@ import { useState, useEffect, useCallback, useRef, useMemo } from 'react'
 import DOM from 'react-dom'
 import Markdown from 'react-markdown'
 import remarkGfm from 'remark-gfm'
+import remarkBreaks from 'remark-breaks'
 import { Plus, Trash2, Pin, PinOff, Pencil, X, Check, StickyNote, Settings, ExternalLink, Maximize2, Loader2 } from 'lucide-react'
 import { collabApi } from '../../api/client'
 import { getAuthUrl } from '../../api/authUrl'
@@ -845,7 +846,7 @@ function NoteCard({ note, currentUser, canEdit, onUpdate, onDelete, onEdit, onVi
                 maxHeight: '4.5em', overflow: 'hidden',
                 wordBreak: 'break-word', fontFamily: FONT,
               }}>
-                <Markdown remarkPlugins={[remarkGfm]}>{note.content}</Markdown>
+                <Markdown remarkPlugins={[remarkGfm, remarkBreaks]}>{note.content}</Markdown>
               </div>
             )}
           </div>
@@ -1352,7 +1353,7 @@ export default function CollabNotes({ tripId, currentUser }: CollabNotesProps) {
               </div>
             </div>
             <div className="collab-note-md-full" style={{ padding: '16px 20px', overflowY: 'auto', fontSize: 14, color: 'var(--text-primary)', lineHeight: 1.7 }}>
-              <Markdown remarkPlugins={[remarkGfm]}>{viewingNote.content || ''}</Markdown>
+              <Markdown remarkPlugins={[remarkGfm, remarkBreaks]}>{viewingNote.content || ''}</Markdown>
               {(viewingNote.attachments || []).length > 0 && (
                 <div style={{ marginTop: 16, paddingTop: 16, borderTop: '1px solid var(--border-primary)' }}>
                   <div style={{ fontSize: 11, fontWeight: 600, color: 'var(--text-faint)', textTransform: 'uppercase', letterSpacing: 0.5, marginBottom: 10 }}>{t('files.title')}</div>