Native-feel pass: PWA integration, system back, offline, haptics, undo

Mobile only (<=639px / coarse pointers); desktop keeps its behaviour.

System integration
- Manifest: id, display_override, monochrome icon, Make my homework
  shortcut and a share target (text/URL via GET, files via POST).
  iOS startup images for the common iPhone sizes. Pinch-zoom is allowed
  again (double-tap zoom is disabled via touch-action instead).
- Share target: /share chooser with New deck / Make my homework; POSTed
  files wait in a 10-minute in-memory store, reach the wizard through
  sessionStorage and never touch disk.
- Web Share: Share rows for decks (JSON file where supported) and the
  homework result, with a clipboard fallback and a toast.
- Offline: a quiet pill appears and Freeze / mode cards are disabled
  with a clear reason; input is never lost (error cards keep Retry).
- State: wizard drafts (text, options, photos up to a size budget)
  survive reloads and OS kills and are cleared on success; re-tapping
  the active tab scrolls to the top; the deck page shows a skeleton
  instead of a spinner.

Navigation and gestures
- System Back closes the topmost layer first: a small history-entry
  stack (lib/use-back-close.ts) covers the drawer, Settings sheet,
  install sheet, deck actions panel and one wizard step; navigations
  are never rewound and stale entries are skipped.
- Destructive-but-reversible actions use Undo toasts: deleting a deck
  (no confirm) and removing a file in the wizard. Irreversible ones
  keep their confirm.

Input and feedback
- Every phone input got inputmode / enterkeyhint / autocomplete /
  autocapitalize / spellcheck; Enter on the last field advances the
  wizard; a clipboard-paste button appears where the API exists.
- Haptics behind a Settings toggle (on by default): tab switches,
  toggles, correct/wrong, completion; Vibration API + the iOS hidden
  switch tick, throttled and silent everywhere else.
- Wake lock during the study feed and homework guide, released on
  leave and re-acquired when the tab returns.

Verified: new native suite 35/35 (manifest/head/viewport, offline,
share target GET + POST, back-gesture layers, undo, share fallback,
tab re-tap, haptics persistence, draft restore), regression 74/74,
mobile 52/52, wizard 80/80, declutter 116/116, animation 8/8,
i18n 25/25. Lint + build clean. SW freezmo-v23.

Needs a real device (documented in the README): iOS haptic tick,
system share sheet entry, wake-lock grant, iPhone startup images,
iOS edge-swipe back, install prompts. Pull-to-refresh and the app
badge were skipped on purpose.

lib/i18n-dict.ts

@@ -148,6 +148,26 @@ const en: Record<string, string> = {
   "settings.details": "Details",
   "settings.privacyLine": "Your key stays in this browser.",
   "settings.recheck": "Re-check connection",
+  "settings.haptics": "Haptics",
+  "settings.hapticsNote": "Vibration feedback on supported phones.",
+
+  /* offline / share / toasts ---------------------------------------- */
+  "offline.banner": "You're offline — saved decks still work.",
+  "offline.generate": "You're offline — connect to generate.",
+  "share.title": "Add to Freezmo",
+  "share.intro": "What should I do with this?",
+  "share.preview": "Shared content",
+  "share.loading": "Loading the shared content…",
+  "share.expired": "That share expired — try again.",
+  "share.tooLarge": "That's too large to share (max 30 MB).",
+  "share.nothing": "Nothing to add.",
+  "share.copied": "Copied to the clipboard.",
+  "share.failed": "Sharing isn't available here.",
+  "toast.deckDeleted": "Deck deleted",
+  "toast.fileRemoved": "File removed",
+  "toast.undo": "Undo",
+  "upload.pasteClipboard": "Paste from clipboard",
+  "upload.clipboardDenied": "Clipboard access was denied.",
 
   /* health ---------------------------------------------------------- */
   "health.ok": "Ollama is reachable and both models are available.",
@@ -300,6 +320,7 @@ const en: Record<string, string> = {
   "deck.titleLabel": "Deck title",
   "deck.rename": "Rename",
   "deck.export": "Export JSON",
+  "deck.share": "Share",
   "deck.regenerate": "Regenerate deck",
   "deck.reallyDelete": "Really delete",
   "deck.delete": "Delete deck",
@@ -777,6 +798,26 @@ const cs: Record<string, string> = {
   "settings.details": "Podrobnosti",
   "settings.privacyLine": "Tvůj klíč zůstává v tomto prohlížeči.",
   "settings.recheck": "Zkontrolovat připojení",
+  "settings.haptics": "Haptika",
+  "settings.hapticsNote": "Vibrace na podporovaných telefonech.",
+
+  /* offline / share / toasts ---------------------------------------- */
+  "offline.banner": "Jsi offline — uložené sady fungují dál.",
+  "offline.generate": "Jsi offline — pro vytvoření se připoj.",
+  "share.title": "Přidat do Freezma",
+  "share.intro": "Co s tím mám udělat?",
+  "share.preview": "Sdílený obsah",
+  "share.loading": "Načítám sdílený obsah…",
+  "share.expired": "Sdílení vypršelo — zkus to znovu.",
+  "share.tooLarge": "To je příliš velké (max 30 MB).",
+  "share.nothing": "Není co přidat.",
+  "share.copied": "Zkopírováno do schránky.",
+  "share.failed": "Sdílení tu není dostupné.",
+  "toast.deckDeleted": "Sada smazána",
+  "toast.fileRemoved": "Soubor odebrán",
+  "toast.undo": "Vrátit",
+  "upload.pasteClipboard": "Vložit ze schránky",
+  "upload.clipboardDenied": "Přístup ke schránce byl zamítnut.",
 
   /* health ---------------------------------------------------------- */
   "health.ok": "Ollama je dostupná a oba modely jsou k dispozici.",
@@ -929,6 +970,7 @@ const cs: Record<string, string> = {
   "deck.titleLabel": "Název sady",
   "deck.rename": "Přejmenovat",
   "deck.export": "Exportovat JSON",
+  "deck.share": "Sdílet",
   "deck.regenerate": "Znovu vytvořit sadu",
   "deck.reallyDelete": "Opravdu smazat",
   "deck.delete": "Smazat sadu",