fix(ws): accept same-origin WebSocket connections in default Origin allow-list

When `cors_origins` was unset, the WS endpoint only allowed
`http://localhost:<port>` and `http://127.0.0.1:<port>` as origins, so a
browser opening the UI via the LAN IP (e.g. `http://192.168.2.100:8765`
when bound to `0.0.0.0`) had its WebSocket closed with code 4003 and
never recovered — leaving the Web UI in a permanent reconnect loop.

Also accept any `Origin` whose authority matches the request's `Host`
header (both `http://` and `https://` schemes). Same-origin is by
definition not CSWSH, so the cross-origin defence added in v0.3.0
remains intact for genuine third-party LAN pages.

media_server/routes/media.py

@@ -414,8 +414,13 @@ async def websocket_endpoint(
             accept_subprotocol = proto
             break
     effective_token = subprotocol_token or token
-    # Origin check — block CSWSH from third-party LAN pages. We accept the same
-    # set of origins as CORS plus the default localhost loopback.
+    # Origin check — block CSWSH from third-party LAN pages. Accept the same
+    # set of origins as CORS plus the default localhost loopback, AND any
+    # same-origin connection (where Origin matches the request's Host header).
+    # Same-origin is inherently safe from CSWSH because CSWSH is a *cross*-
+    # origin attack — without this, binding to 0.0.0.0 and accessing the UI
+    # via a LAN IP would have its WebSocket rejected by the browser-sent
+    # Origin, which the static allowlist can't anticipate.
     allowed_origins = set(
         settings.cors_origins
         or [
@@ -427,8 +432,17 @@ async def websocket_endpoint(
     # Same-origin connections from native apps may omit Origin entirely; only
     # reject when an Origin is present AND not in the allow-list.
     if origin is not None and origin not in allowed_origins:
-        await websocket.close(code=4003, reason="Origin not allowed")
-        return
+        host_header = websocket.headers.get("host", "")
+        # Origin uses http/https; match against both scheme variants of Host
+        # so HTTPS deployments without an explicit cors_origins still work.
+        same_origin_candidates = (
+            {f"http://{host_header}", f"https://{host_header}"}
+            if host_header
+            else set()
+        )
+        if origin not in same_origin_candidates:
+            await websocket.close(code=4003, reason="Origin not allowed")
+            return
 
     # Verify token
     from ..auth import auth_enabled, get_token_label, token_label_var