[yashiels]

Closes #129

PR2 of the Oracle-approved PWA plan (docs/pwa-plan.md).

What

• Replace handwritten public/sw.js with Serwist 10 built via @serwist/build injectManifest + esbuild (scripts/build-sw.mjs, runs after next build)
• Routing policy per plan: analytics/vidsrc origins + RSC Flight requests + TMDB API = NetworkOnly; static /_next assets cache-first; TMDB images cache-first bounded (300 entries, 14 days, statuses [0,200]); navigation fallback to /offline
• Static /offline page (OfflineClient + styles)
• Update flow: skipWaiting:false / clientsClaim:true, armed-reload UpdateToast on waiting worker + SKIP_WAITING message channel, sw.js served with updateViaCache:no-store registration
• Old cache cleanup on activate (skystream-v1 legacy)
• eslint: built public/sw.js ignored, VIDSRC_ORIGIN build global declared for src/sw

Verification

• pnpm test: 26 suites, 363 passed (53 new SW tests)
• pnpm run lint: 0 errors, 4 pre-existing warnings
• pnpm build: succeeds, [build-sw] wrote public/sw.js (14 precached URLs)
• git diff origin/main: zero added comments

[sentinel-skyner]

🛡️ Sentinel review

Found 1 clear maintainability issue.

1 inline comment below.

_{Automated review via cursorbridge:gpt-5.3-codex. Findings only — not an approval. Push new commits to re-review.}

[sentinel-skyner]

🛡️ Low public/sw.js is marked as generated/ignored, but this PR still modifies that file as a tracked artifact. .gitignore does not apply to already tracked files, so builds will continue to produce churn in git and can cause accidental commits of regenerated output.