refactor(settings): drop jellyfin machine service + dead machine path fields

Slice 1 of jellyfin-service-registry. Jellyfin is configured exclusively
via the service registry now; the machine-level media_root/path_prefix
fields were dead duplicates of the global config.

- services/settings_store.py: DEFAULT_SERVICES no longer includes
  "jellyfin" (now ["monitoring", "files"]). Removed machine-level
  media_root/path_prefix from _default_local_machine, _row_to_machine,
  _normalize_machine_payload, _seed_local_machine, get_machine_config,
  and upsert_machine. _default_local_machine no longer reads global
  config, so the get_settings import is dropped.
- routers/settings.py: removed media_root/path_prefix from
  MonitoringMachineInput (dead API input; store already ignored them).

The global config remote_media_root/path_prefix properties + path_utils.py
are unchanged (files.py and media_index still use them for Jellyfin->SSH
path resolution). ruff clean; 239 backend tests pass.

backend/src/media_library_viewer_api/.pi-map.md

@@ -4,7 +4,7 @@ dir: backend/src/media_library_viewer_api
 index: backend/src/media_library_viewer_api/.pi-map.index.md
 
 ## role
-FastAPI backend providing authenticated media library viewing APIs with Jellyfin/Jellyseerr integration, remote SSH job execution, and observability features.
+FastAPI backend providing authenticated API endpoints and remote SSH job execution for viewing and managing media library metadata from Jellyfin/Jellyseerr services.
 ## files
 - __init__.py | Swaps the position of two tmux panes within a window or between windows | dep: tmux, sh
 - auth.py | Implements OIDC/JWT and API key authentication for a FastAPI backend with middleware-based route protection. | exp: func:_normalize_issuer_url(issuer_url: str) → str, call:issuer_url.rstrip, func:get_oidc_metadata(issuer_url: str) → dict[str, Any], call:_normalize_issuer_url, call:urljoin, call:requests.get, call:response.raise_for_status, call:response.json, call:isinstance, raise:RuntimeError, func:get_jwk_client(jwks_url: str) → PyJWKClient, call:PyJWKClient, func:_split_audience(audience: str) → list[str], call:item.strip, call:audience.split, func:validate_auth_settings(settings: Settings) → None, raise:RuntimeError, func:validate_bearer_jwt(authorization: str | None, settings) → dict[str, Any], call:get_settings, call:validate_auth_settings, call:authorization.partition, call:scheme.lower, call:token.strip, call:_normalize_issuer_url, call:get_oidc_metadata, call:settings.oidc_jwks_url.strip, call:str, call:metadata.get, call:get_jwk_client, call:jwk_client.get_signing_key_from_jwt, call:_split_audience, call:jwt.decode, call:list, call:len, call:int, raise:PermissionError, raise:RuntimeError, func:require_jwt_auth(request: Request, call_next), call:get_settings, call:path.startswith, call:call_next, call:validate_bearer_jwt, call:request.headers.get, call:logger.warning, call:JSONResponse, call:str, call:logger.exception, call:claims.get, call:isinstance, func:get_api_key() → str, call:get_settings_store, call:store.get_settings, call:settings.get, call:secrets.token_urlsafe, call:store.update_setting, func:require_api_key(authorization) → str, call:get_api_key, call:secrets.compare_digest, raise:HTTPException | dep: logging, secrets, functools, typing, urllib.parse, jwt, requests, fastapi, fastapi.responses, jwt.exceptions, media_library_viewer_api.config, media_library_viewer_api.dependencies
@@ -18,7 +18,7 @@ FastAPI backend providing authenticated media library viewing APIs with Jellyfin
 - utils.py | Provides UI-framework-independent formatting helpers and ffprobe output summarizers for video, audio, and subtitle streams. | exp: func:ticks_to_minutes(ticks: int | None) → int | None, call:round, func:human_size(num: int | float | None) → str, call:float, call:int, func:timestamp_to_local(ts: float | None) → str, call:datetime.fromtimestamp(ts).strftime, func:is_known_video_file(path: str | None) → bool, call:PurePosixPath(path).suffix.lower, func:format_duration(seconds: str | int | float | None) → str, call:float, call:str, call:int, func:format_bitrate(bit_rate: str | int | float | None) → str, call:float, call:str, func:_tags(stream: dict[str, Any]) → dict[str, Any], call:stream.get, func:_disposition(stream: dict[str, Any], key: str) → str, call:(stream.get("disposition") or {}).get, call:stream.get, func:_side_data_types(stream: dict[str, Any]) → str, call:stream.get, call:item.get, call:values.append, call:", ".join, func:ffprobe_format_summary(ffprobe: dict[str, Any]) → dict[str, str], call:ffprobe.get, call:fmt.get, call:format_duration, call:human_size, call:float, call:format_bitrate, call:str, func:summarize_video_streams(ffprobe: dict[str, Any]) → list[dict[str, Any]], call:ffprobe.get, call:stream.get, call:_tags, call:rows.append, call:format_bitrate, call:_side_data_types, call:tags.get, call:_disposition, func:summarize_audio_streams(ffprobe: dict[str, Any]) → list[dict[str, Any]], call:ffprobe.get, call:stream.get, call:_tags, call:rows.append, call:format_bitrate, call:tags.get, call:_disposition, func:summarize_subtitle_streams(ffprobe: dict[str, Any]) → list[dict[str, Any]], call:ffprobe.get, call:stream.get, call:_tags, call:rows.append, call:tags.get, call:_disposition, func:summarize_streams(ffprobe: dict[str, Any]) → list[dict[str, Any]], call:ffprobe.get, call:rows.append, call:format_bitrate, call:stream.get("tags", {}).get | dep: datetime, pathlib, typing
 - version.py | Provides version retrieval and formatting utilities for a backend service, falling back through environment variables, package metadata, and default values. | exp: func:get_backend_version() → str, call:os.getenv("APP_VERSION", "").strip, call:package_version, func:get_backend_build_info() → str, call:os.getenv("APP_BUILD_INFO", "").strip, call:os.getenv("GIT_COMMIT", "").strip, call:os.getenv("BUILD_COMMIT", "").strip, func:format_version_label(version: str, build_info: str) → str, call:version.strip, call:build_info.strip, func:get_version_info() → dict[str, str], call:get_backend_version, call:get_backend_build_info, call:format_version_label | dep: os, importlib.metadata
 ## arch
-Layered FastAPI architecture using dependency injection, pydantic-settings configuration, OIDC/API-key middleware authentication, template-based remote execution, and Prometheus/structured logging observability.
+Layered FastAPI architecture using dependency injection (providers/clients), Pydantic settings configuration, OIDC/API-key middleware authentication, and template-based remote SSH execution with structured observability (Prometheus/JSON logging).
 ## tags
 call:, settings, call:get, request, get, client, call:str, id
 ## symbols