Web UI: fix Plex status text, PLEX_URL/PLEX_TOKEN env, local stem server auto-detect, WEB=0

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

server/README.md

@@ -43,6 +43,9 @@ curl http://192.168.86.2:8765/api/info
 | `TOKEN`     | empty    | If set, requests need `X-Stem-Token` or `?token=`           |
 | `INDEX_TTL` | `30`     | Seconds between rescans of the stems folder                |
 | `QUEUE_DIR` | `/queue` | stemd's Stem Now folder (`stemd/state/queue` on unraid)    |
+| `PLEX_URL`  | empty    | Plex address, passed to the web UI via `/api/config`       |
+| `PLEX_TOKEN`| empty    | Plex token for the web UI (set `TOKEN` too)                |
+| `WEB`       | `1`      | `0` turns off the web UI                                   |
 
 ## API