fix(i18n): every language says one file and five files its own way

Finishes the plural work the previous wip commit started. t() picks a
count string's form by the language's own Intl.PluralRules, and every
locale now spells out the forms its language reaches with whole
numbers, about 160 count strings in all: one, few and many in Russian,
Ukrainian and Polish, one and few in Czech and Slovak, five forms in
Arabic, one in the others, none in Japanese, Korean, Chinese, Thai,
Vietnamese and Indonesian. Each language was translated and then
reviewed on its own. English no longer reads "1 files", "1 updates
available" or "photo(s)".

Count labels shown next to a number now take that number too: the
atlas and admin statistics, the trip cards, journey and shared trip
pills, packing templates, receipts, storage usage, the Studio export
note. A heading that shared its key with a counted label keeps a key of
its own (the boarding pass heading, the Bookings tab), so languages that
put a noun after a number in the singular keep a plural heading. The
plugin hosts chip passed its count through .replace() after t() and
never got a form; three toasts sent the count as text. Mail and push
texts for shared photos and suppressed storage failures pick their form
in code through pluralForm.

A whole number sent as text counts too, which is how in-app
notification params arrive, and the plural rule follows the language of
the strings on screen while another one still loads.

The parity check knows which forms each language needs and refuses
missing and impossible ones. It also reads keys that contain a colon
now: it skipped them, which hid 58 missing plugin permission texts in
Catalan and 35 in Vietnamese, both translated. The client parity test
covers every language of the registry instead of a hand-kept list of 19,
and the placeholder spec lets a form spell its number out only where
its category is that one number. Brazilian Portuguese error screens
were in Breton, and an Arabic dashboard label held Hebrew text.

client/src/components/Packing/ApplyTemplateButton.tsx

@@ -92,7 +92,7 @@ export default function ApplyTemplateButton({ tripId, visibility, style, classNa
               <div style={{ flex: 1, textAlign: 'start' }}>
                 <div style={{ fontWeight: 600 }}>{tmpl.name}</div>
                 <div style={{ fontSize: 'calc(10px * var(--fs-scale-caption, 1))', color: 'var(--text-faint)' }}>
-                  {tmpl.item_count} {t('admin.packingTemplates.items')}
+                  {tmpl.item_count} {t('admin.packingTemplates.items', { count: tmpl.item_count })}
                 </div>
               </div>
             </button>

client/src/components/Packing/PackingListPanelBagCard.tsx

@@ -125,7 +125,7 @@ export function BagCard({ bag, bagItems, totalWeight, pct, tripId, tripMembers,
         <div style={{ height: '100%', borderRadius: 99, background: bag.color, width: `${pct}%`, transition: 'width 0.3s' }} />
       </div>
       <div style={{ display: 'flex', alignItems: 'center', justifyContent: 'space-between', gap: 8, marginTop: 5 }}>
-        <span style={{ fontSize: sz.count, color: 'var(--text-faint)' }}>{bagItems.length} {t('admin.packingTemplates.items')}</span>
+        <span style={{ fontSize: sz.count, color: 'var(--text-faint)' }}>{bagItems.length} {t('admin.packingTemplates.items', { count: bagItems.length })}</span>
         <span style={{ fontSize: sz.weight, color: 'var(--text-muted)', fontWeight: 600, display: 'inline-flex', alignItems: 'center', gap: 3, fontVariantNumeric: 'tabular-nums' }}>
           {totalWeight >= 1000 ? `${(totalWeight / 1000).toFixed(1)} kg` : `${totalWeight} g`}
           {editingLimit && canEdit ? (

client/src/components/Packing/PackingListPanelBagModal.tsx

@@ -59,7 +59,7 @@ export function BagModal(S: PackingState) {
                   {unassignedWeight >= 1000 ? `${(unassignedWeight / 1000).toFixed(1)} kg` : `${unassignedWeight} g`}
                 </span>
               </div>
-              <div style={{ fontSize: 'calc(11px * var(--fs-scale-caption, 1))', color: 'var(--text-faint)' }}>{unassigned.length} {t('admin.packingTemplates.items')}</div>
+              <div style={{ fontSize: 'calc(11px * var(--fs-scale-caption, 1))', color: 'var(--text-faint)' }}>{unassigned.length} {t('admin.packingTemplates.items', { count: unassigned.length })}</div>
             </div>
           )
         })()}

client/src/components/Packing/PackingListPanelBagSidebar.tsx

@@ -85,7 +85,7 @@ export function BagSidebar(S: PackingState) {
             <div style={{ ...hairline(bags.length === 0), display: 'flex', alignItems: 'center', gap: 6, padding: '11px 0' }}>
               <span style={{ width: 10, height: 10, borderRadius: '50%', border: '1.5px dashed var(--text-faint)', flexShrink: 0 }} />
               <span style={{ fontSize: 'calc(12px * var(--fs-scale-body, 1))', fontWeight: 600, color: 'var(--text-muted)' }}>{t('packing.noBag')}</span>
-              <span title={`${unassigned.length} ${t('admin.packingTemplates.items')}`} style={{ fontSize: 'calc(10px * var(--fs-scale-caption, 1))', fontWeight: 700, padding: '1px 6px', borderRadius: 99, minWidth: 18, textAlign: 'center', background: 'var(--bg-tertiary)', color: 'var(--text-faint)', fontVariantNumeric: 'tabular-nums' }}>{unassigned.length}</span>
+              <span title={`${unassigned.length} ${t('admin.packingTemplates.items', { count: unassigned.length })}`} style={{ fontSize: 'calc(10px * var(--fs-scale-caption, 1))', fontWeight: 700, padding: '1px 6px', borderRadius: 99, minWidth: 18, textAlign: 'center', background: 'var(--bg-tertiary)', color: 'var(--text-faint)', fontVariantNumeric: 'tabular-nums' }}>{unassigned.length}</span>
               <span style={{ flex: 1 }} />
               <span style={{ fontSize: 'calc(11px * var(--fs-scale-caption, 1))', fontWeight: 600, color: 'var(--text-muted)', fontVariantNumeric: 'tabular-nums' }}>{kgOrG(unassignedWeight)}</span>
             </div>

client/src/components/Packing/PackingListPanelHeader.tsx

@@ -76,7 +76,7 @@ export function PackingHeader(S: PackingState) {
                       <Package size={13} className="text-content-faint" />
                       <div style={{ flex: 1, textAlign: 'start' }}>
                         <div style={{ fontWeight: 600 }}>{tmpl.name}</div>
-                        <div style={{ fontSize: 'calc(10px * var(--fs-scale-caption, 1))', color: 'var(--text-faint)' }}>{tmpl.item_count} {t('admin.packingTemplates.items')}</div>
+                        <div style={{ fontSize: 'calc(10px * var(--fs-scale-caption, 1))', color: 'var(--text-faint)' }}>{tmpl.item_count} {t('admin.packingTemplates.items', { count: tmpl.item_count })}</div>
                       </div>
                     </button>
                   ))}

client/src/components/Packing/usePackingListPanel.test.tsx

@@ -621,7 +621,7 @@ describe('usePackingList — templates, import and signals', () => {
     await act(async () => { await result.current.handleApplyTemplate(2) })
 
     expect(useTripStore.getState().packingItems).toContainEqual(fresh)
-    expect(toastSpy).toHaveBeenCalledWith('1 items added from template', 'success', undefined)
+    expect(toastSpy).toHaveBeenCalledWith('1 item added from template', 'success', undefined)
     expect(result.current.showTemplateDropdown).toBe(false)
     expect(result.current.applyingTemplate).toBe(false)
   })
@@ -700,7 +700,7 @@ describe('usePackingList — templates, import and signals', () => {
     await act(async () => { await result.current.handleBulkImport() })
 
     expect(useTripStore.getState().packingItems).toContainEqual(imported)
-    expect(toastSpy).toHaveBeenCalledWith('1 items imported', 'success', undefined)
+    expect(toastSpy).toHaveBeenCalledWith('1 item imported', 'success', undefined)
     expect(result.current.importText).toBe('')
     expect(result.current.showImportModal).toBe(false)
   })