stemd: AUTO_SCAN=0 runs on request only (Stem Now)

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

README.md

@@ -123,6 +123,7 @@ To update, copy the new files, rebuild, `docker rm -f` the container and run it
 | `MODEL` | `roformer_bs_sw` | Any id from [the model table](#separation-models) |
 | `DEVICE` | `cuda` | `cuda`, `cuda:N` or `cpu` |
 | `RESCAN_MIN` | `30` | Minutes between library scans once caught up |
+| `AUTO_SCAN` | `1` | `0` to skip library scans and only separate Stem Now requests |
 | `FP16` | `1` | Half precision on the GPU (`0` for fp32) |
 | `OVERLAP`, `SEGMENT`, `SHIFTS` | `0.25`, `0`, `0` | Separation quality, same as the desktop app |