Slice 4b backend half. Jellyfin and Jellyseerr clients are now resolved from
service instances instead of machine-level app config.
- Add jellyseerr service definition (6 service types total); add user_id to
the Jellyfin service config.
- dependencies.py: jellyfin_service_id query param + _service_record
(decrypt-on-read); get_jellyfin_client / get_jellyseerr_client / get_user_id
resolve against the service registry (first enabled instance as fallback).
- SSH/Files transport (get_ssh_client) unchanged; still uses machine_id.
- Update service-registry tests for 6 types.
Selection model: split params — ?jellyfin_service_id= for Jellyfin/Jellyseerr,
?machine_id= for SSH/Files. Frontend threading follows in the next PR.
Verification: backend ruff clean, pytest 222 passed; frontend green (unchanged).
Developer
8ff735d644