feat: consolidate on the shadcn frontend and harden playback

Frontend
- Replace the Ant Design app with the shadcn/ui app as the single frontend,
  keeping the portfolio side-by-side revertible in this commit.
- Drop the abandoned mdui experiment and the AntD tree so there is one app,
  one router and one design system to maintain.

Live playback
- Stop racing the encoder. lowLatencyMode + liveSyncDurationCount:1 targeted a
  single 4s segment, so playback ran at up to 1.10x and the forward buffer
  bottomed out at 0.1s, re-buffering every segment. Measured over 40s:
  buffer min 0.1s -> 8.9s, rate 1.00 constant, 0 stalls.
- Remove the 落后 labels and the page-level edge-snapping timer that fought
  hls.js over two different definitions of "latency".
- Live can no longer be paused: the control is not rendered while it plays, so
  the icon can never misreport state.
- Fix autoplay: muted autoplay started silently and never unmuted, and the
  gesture that restored sound also toggled playback off. One owner now.

Source ("原画") rendition
- Publish the publisher's stream remuxed losslessly via -c:v copy alongside the
  transcoded ones, so a source option exists even when every ladder entry
  downsizes.
- Give renditions an ASCII path slug: the HLS path is part of the URL and
  MediaMTX rejects non-alphanumeric paths, so 原画 could never be served.

Backend
- Supervise MediaMTX from the backend: start it at boot and restart it on exit,
  never killing an origin it did not start.
- Clear stale HLS output before restarting an encoder; an ENDLIST-less playlist
  left by a dead encoder hangs hls.js forever.
- Mark JSON timestamps as UTC. utcnow().isoformat() emitted a naive string that
  JS read as local time, so every viewer heartbeat looked 8 hours old in UTC+8
  and the live board's active-viewer count was permanently zero.
- Rebind a viewer session when it arrives on another stream instead of failing,
  and survive the StrictMode double-heartbeat race on first insert.
- Replace the Linux-only /proc and os.getloadavg metrics with psutil.
- Complete MediaMTX's cookieCheck redirect inside /hls proxying, and hold the
  httpx client open for the streamed body.

Housekeeping
- Ignore RainOSS (it stores accessKeySecret), runtime output, TLS keys and
  .venv; remove generated screenshots, load test scripts and stray files.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

DEPLOYMENT.md

@@ -14,43 +14,45 @@ Run these commands from PowerShell on the Windows node.
 
 ### 1. Install prerequisites
 
-Required on PATH: Python 3.11+, Node.js LTS with npm, FFmpeg, and MediaMTX unless starting with -NoMediaMTX. Optional for GPU verification: NVIDIA driver and nvidia-smi.
+Required on PATH: Python 3.11+, FFmpeg, and MediaMTX. MediaMTX may instead be left in the repository's `mediamtx\` directory, which is where the backend looks second. Node.js is only needed to build the frontend for deployment.
 
 ### 2. Install application dependencies
 
 ```powershell
-powershell -ExecutionPolicy Bypass -File .\start.ps1 -InstallDeps -NoMediaMTX
+powershell -ExecutionPolicy Bypass -File .\start.ps1 -InstallDeps
 ```
 
-### 3. Start the full Windows stack
+### 3. Start the stack
 
 ```powershell
 powershell -ExecutionPolicy Bypass -File .\start.ps1
 ```
 
-This starts MediaMTX origin, FastAPI backend on 0.0.0.0:8080, Vite frontend on 0.0.0.0:5173, HLS output under runtime\hls, and logs under runtime\logs.
+This starts the FastAPI backend on 0.0.0.0:8080. The backend owns everything else:
 
-Open backend docs at http://127.0.0.1:8080/docs and frontend UI at http://127.0.0.1:5173/. Publish RTMP to rtmp://127.0.0.1:1935/live/<stream_key>. MediaMTX HLS is http://127.0.0.1:8888/<stream_key>/index.m3u8.
+- **MediaMTX** is started at boot if nothing is already answering its API on :9997, and restarted by the supervisor if it dies. Set `LS_MEDIA_ORIGIN_AUTOSTART=false` to manage it externally; the backend then only supervises transcoders.
+- **Transcoders** are started for every live stream whose MediaMTX path is publishing, and restarted within ~10s of an ffmpeg process exiting.
+- **HLS** is written under `runtime\hls` and served through `GET /hls/...`, which falls back to proxying MediaMTX's own HLS when the local files are absent.
 
-### 4. Useful Windows variants
+Publish RTMP to rtmp://127.0.0.1:1935/live/<stream_key>. Backend docs are at http://127.0.0.1:8080/docs.
+
+### 4. Useful variants
 
 ```powershell
-powershell -ExecutionPolicy Bypass -File .\start.ps1 -NoMediaMTX
-powershell -ExecutionPolicy Bypass -File .\start.ps1 -NoFrontend
-powershell -ExecutionPolicy Bypass -File .\start.ps1 -HostAddress 0.0.0.0 -BackendPort 8080 -FrontendPort 5173
+powershell -ExecutionPolicy Bypass -File .\start.ps1 -HostAddress 0.0.0.0 -BackendPort 8080
 ```
 
 ### 5. Smoke test commands
 
 ```powershell
-curl.exe -I http://127.0.0.1:5173/
 curl.exe http://127.0.0.1:8080/api/health
+curl.exe http://127.0.0.1:9997/v3/paths/list
 ffmpeg -version
 mediamtx --version
 nvidia-smi
 ```
 
-If browser or network tests run from another machine, open the Windows firewall for ports 5173, 8080, 1935, and 8888.
+If browser or network tests run from another machine, open the Windows firewall for ports 8080, 1935, and 8888.
 
 ## Windows edge node launcher
 
@@ -82,4 +84,4 @@ Replay records store paths relative to LS_REPLAY_MEDIA_DIR. Absolute paths and p
 
 ## Linux and macOS
 
-Linux and macOS are not the primary deployment path. For local development, run the backend with uvicorn from backend, run the frontend with npm run dev from frontend, and set LS_HLS_RUNTIME_DIR to a writable directory.
+Linux and macOS are not the primary deployment path. For local development, run the backend with uvicorn from `backend`, run the frontend with `npm run dev` from `frontend`, and set `LS_HLS_RUNTIME_DIR` to a writable directory.