Implement PWA shell (task 50)

Add web manifest, placeholder icons, app-shell service worker, and
install prompt so famapp is installable on iOS and Android home screens.

- public/manifest.webmanifest — name, short_name, standalone display,
  start_url /, all four icon sizes (192/384/512 + maskable)
- public/icon-{180,192,384,512,512-maskable}.png — indigo placeholder
  squares generated by scripts/generate-icons.mjs (pnpm gen:icons)
- public/icon.svg — house-icon SVG source for future branded export
- public/sw.js — hand-rolled app-shell SW: precaches offline.html,
  cache-first for /_next/static/, network-first navigation with offline
  fallback, network-only for /api/*
- public/offline.html — branded offline fallback page
- src/components/pwa-register.tsx — client SW registration
- src/components/install-prompt.tsx — dismissible install banner:
  beforeinstallprompt on Android, "Add to Home Screen" hint on iOS
- Root layout: viewport themeColor, manifest/appleWebApp metadata,
  apple-touch-icon, mounts PwaRegister + InstallPrompt

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

STATUS.md

@@ -27,6 +27,8 @@ Living progress tracker. Update at the end of each task. Codex and Claude Code b
 - **26 — Customizable layout + widget configuration**. Installed `react-grid-layout` v2. Dashboard pages check `?edit=1` to enter edit mode, rendering a client `DashboardEditor` instead of the static grid. Editor uses `react-grid-layout` with `gridConfig`/`dragConfig` v2 API; each widget shell shows a drag handle, configure button (⚙), and remove button (🗑). `WidgetPicker` is a two-step modal: step 1 lists all registry widgets grouped by category; step 2 is a `WidgetConfigurator` auto-generated from the widget's default config — handles `"all"|string[]` multi-selects, booleans, numbers, and enums. `resolveWidgetConfigOptions` server action fetches dynamic options (calendars, lists). Save validates each config against its registered Zod schema. Reset to defaults calls `computeDefaultLayout()`. `pnpm typecheck`, `pnpm build` pass.
 - **31 — Public share viewer**. Made `actorId` nullable in `activity_log` (migration `0010_nullable_actor_id.sql`, `onDelete: "set null"`) for anonymous share-page mutations. Added `logShareActivity` to `_core/activity.ts` (no session, explicit `householdId`). Added `householdId` to `resolveShareToken` return. Added `renderSharedView` to `EntityTypeRegistration` type. Each module implements `loadForShare` (bare DB queries, no session) and `renderSharedView`: calendar shows upcoming 90-day events or single-event details, lists shows items with optional toggle, notes shows title + body. `toggleShareListItem` server action lives in `lists/server/share-actions.ts` — validates token write capability, verifies item→list→household chain, logs `share.toggle` with `actorId = null`. `/app/s/[token]/page.tsx` resolves token, dispatches to `loadForShare` + `renderSharedView`, returns friendly error for invalid/expired tokens, sets `noindex`. Middleware `/s/*` exemption confirmed present. `pnpm typecheck`, `pnpm lint`, `pnpm build`, and all 4 E2E specs pass.
 
+- **50 — PWA shell**. `public/manifest.webmanifest` (name, short_name, icons, theme_color, display: standalone, start_url `/`). Placeholder PNG icons at 180, 192, 384, 512 (regular + maskable) generated by `scripts/generate-icons.mjs` (`pnpm gen:icons`); `public/icon.svg` committed as source. Hand-rolled service worker at `public/sw.js`: precaches `offline.html` on install, cache-first for `/_next/static/`, network-first for navigation with offline fallback, network-only for API routes. `src/components/pwa-register.tsx` registers the SW client-side. `src/components/install-prompt.tsx` shows a dismissible banner: `beforeinstallprompt` on Android/Chrome, a one-time "Add to Home Screen" hint on iOS (detected via UA + `navigator.maxTouchPoints`, suppressed in standalone mode). Root layout exports `viewport` (themeColor), updated `metadata` (manifest, appleWebApp, apple-touch-icon), and mounts both new components. `pnpm typecheck`, `pnpm lint`, `pnpm build` all clean.
+
 ## Next up
 
 - Next task in `docs/tasks/`.