Add PWA, CLI daemon, deploy tooling, and full documentation

PWA (pwa/):
- Ephemeral QR pairing and trusted device direct reconnect (no QR re-scan)
- Known devices tab as default; pairRoomName() derives deterministic room
- In-app QR scanner via native BarcodeDetector API
- Multi-file send/receive with offer queue and Accept all
- Auto-download on receipt, real-time send/receive progress bars
- Trusted peer nicknames, rename, forget
- Terminal aesthetic: #080808 bg, #00e87a accent, JetBrains Mono
- manifest.json corrected (SVG icon, theme_color, share_target)
- Apple PWA meta tags for home screen install

CLI (cli/):
- flit send / flit recv: ephemeral one-shot transfer with terminal QR
- flit daemon: persistent receiver for trusted peers from ~/.flit/daemon.toml
  - TOML config: signal_url, turn_url, download_dir, [[peers]]
  - One goroutine per peer, exponential backoff reconnect (2s→30s cap)
  - transport.PairRoomName() and Session.OnDisconnected added
- Anchor/TURN config via FLIT_SIGNAL_URL / FLIT_TURN_URL env vars (no hardcoded URLs)

Deploy:
- build-pwa.sh, deploy-pwa.sh / serve-pwa.sh templates in README (gitignored)
- .gitea/workflows/build.yml: PWA build on v* tag, Gitea release artifact
- pwa/public/config.js gitignored; config.js.example committed
- .env.example for CLI env vars

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

.gitea/workflows/build.yml

@@ -0,0 +1,38 @@
+name: Build
+
+on:
+  push:
+    tags:
+      - 'v*'
+  workflow_dispatch:
+
+jobs:
+  build:
+    name: Build & release
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '24'
+
+      - name: Build PWA
+        run: |
+          cd pwa
+          npm ci
+          npm run build
+
+      - name: Package release artifact
+        run: |
+          mkdir -p dist
+          tar -C pwa/dist -czf dist/flit-pwa.tar.gz .
+
+      - name: Create release
+        if: startsWith(github.ref, 'refs/tags/')
+        uses: https://gitea.com/actions/gitea-release-action@main
+        with:
+          token: ${{ secrets.RELEASE_TOKEN }}
+          files: dist/*
+          prerelease: ${{ contains(github.ref_name, '-') }}