feat(frontend): add mobile PWA install support

[KyleTryon]

Summary

• Adds mobile PWA metadata, app icons, service worker caching, and production registration.
• Adds a mobile-only install nudge with native install prompt support and iOS add-to-home guidance.
• Adds dashboard shortcuts for Dashboard, Sources, and Open Video.

Validation

• pnpm preflight

[Copilot]

Pull request overview

Adds Progressive Web App (PWA) install support to the frontend, including manifest/service worker infrastructure and a mobile-only “install” nudge surfaced on the dashboard, plus a shortcut that deep-links into opening local video.

Changes:

• Add PWA runtime utilities (install prompt handling + production SW registration) and corresponding unit tests.
• Introduce a mobile-only dashboard install nudge UI (native prompt on supported browsers; iOS add-to-home guidance otherwise).
• Add PWA assets/metadata (manifest + icons + service worker caching) and a manifest shortcut that triggers openVideo=1, handled on the dashboard route.

Reviewed changes

Copilot reviewed 10 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
apps/frontend/src/routes/_app.dashboard.tsx	Opens the local video dialog when launched via the manifest shortcut query param and cleans up the URL.
apps/frontend/src/main.tsx	Boots PWA install prompt listeners and registers the service worker in production.
apps/frontend/src/lib/pwa.ts	Implements install prompt capture/subscription, dismissal persistence, environment detection, and SW registration.
apps/frontend/src/lib/pwa.test.ts	Adds unit tests for install-mode resolution and dismissal persistence helpers.
apps/frontend/src/components/MobilePwaInstallNudge.tsx	Adds the mobile-only install nudge component and a presentational card for testing.
apps/frontend/src/components/frontendWorkflow.test.ts	Adds coverage for install nudge rendering and ensures it’s not present in default server markup.
apps/frontend/src/components/DashboardScreen.tsx	Renders the install nudge on the dashboard header area.
apps/frontend/public/service-worker.js	Adds basic app-shell + asset caching strategies and cache versioning/cleanup.
apps/frontend/public/manifest.webmanifest	Defines PWA metadata and shortcuts (Dashboard, Sources, Open Video).
apps/frontend/index.html	Adds manifest link and mobile/PWA meta tags (theme color, iOS web-app support).

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