fix(stats): restrict local requests and serve the dashboard over HTTP (#263)

docs-site/immersion-tracking.md

@@ -31,6 +31,28 @@ Episode completion for local `watched` state uses the shared `DEFAULT_MIN_WATCH_
 
 The same immersion data powers the stats dashboard.
 
+The browser dashboard and in-app stats overlay both load from the local HTTP server.
+The server accepts loopback hosts only and rejects requests from other browser origins,
+including opaque origins such as `file://`. API clients without a browser origin can
+still use the local API. Mutation requests with a body must use `application/json`;
+bodyless deletion and Anki browse requests remain supported. Requests rejected by the
+host or origin checks receive `403`; mutation bodies without a JSON content type
+receive `415`.
+
+Use the loopback dashboard URL directly. Reverse-proxied dashboards and Tailscale
+Serve URLs are unsupported because their host or browser origin is not the local
+server's origin. SSH stats synchronization is unchanged.
+
+Scripts sending a JSON body must include the content type. For example, this
+requests a duplicate-line cleanup preview without changing the database. Replace
+the port if you configured a different `stats.serverPort`:
+
+```bash
+curl http://127.0.0.1:6969/api/stats/maintenance/duplicate-lines \
+  -H 'Content-Type: application/json' \
+  -d '{"dryRun":true}'
+```
+
 - In-app overlay: focus the visible overlay, then press the key from `stats.toggleKey` (default: `` ` `` / `Backquote`).
 - Launcher command: run `subminer stats` to start the local stats server on demand (it also opens the dashboard in your browser when `stats.autoOpenBrowser` is enabled; the default is `false`).
 - Background server: run `subminer stats -b` to start or reuse a dedicated background stats daemon without keeping the launcher attached, and `subminer stats -s` to stop that daemon.