scripts: FileBrowser volumes controller-managed, remove drive auto-discovery

- docker-setup.sh install_filebrowser(): removed /mnt/* auto-discovery;
  FileBrowser now installed with no drive volumes. Initial config.yaml
  written with /srv fallback. Controller's SyncFileBrowserMounts() takes
  over on first startup and manages volumes/config going forward.
- Added ./config.yaml bind mount to initial docker-compose.yml so
  FileBrowser starts correctly before controller syncs.
- Fixed ((step_num++)) → step_num=$(( step_num + 1 )) to prevent
  set -euo pipefail trap when var starts at 0 (same class of bug as
  the found_mounts fix in the previous commit).
- scripts/README.md: step 7 updated to reflect controller-managed volumes.
- CHANGELOG.md: added entry for all scripts changes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/README.md

@@ -69,7 +69,7 @@ The script runs these steps in order:
 | 4b | `install_cloudflare_tunnel()` | Deploy Cloudflare Tunnel (optional, only if tunnel token provided in wizard). |
 | 5 | `generate_self_signed_cert()` | Generate self-signed CA + wildcard cert (optional, if `--self-signed-cert` flag set). |
 | 6 | `run_config_wizard()` | Interactive wizard or Hub download. Generates `controller.yaml` with customer settings. |
-| 7 | `install_filebrowser()` | Deploy FileBrowser Quantum with auto-discovered drive mounts (optional). |
+| 7 | `install_filebrowser()` | Deploy FileBrowser Quantum with no drive volumes (optional). Drive volumes are managed by the controller via `SyncFileBrowserMounts()` after storage is registered. |
 | 8 | `install_controller()` | Deploy felhom-controller (privileged container with system access). |
 | 9 | `install_tools_and_configure()` | Install ctop, lazydocker, Docker shell aliases. |