feat(jellyseer): stats backend — provider, stat widgets, router (slice 1/3)

Groundwork for Jellyseerr request stats in the Jellyfin service, behind a
small reusable abstraction so future stats services (Sonarr/Radarr) reuse it.

Backend:
- JellyseerrClient.request_count() -> /api/v1/request/count (normalized
  total/pending/approved/declined/processing/available) and recent_requests()
  -> /api/v1/request mapped to {name,type,status,media_status,created_at}
  with numeric status enums labelled.
- widgets/stats_provider.py: StatsProvider protocol + registry keyed by
  service_type (StatValue/StatsResult). A thin generic interface.
- widgets/jellyseerr_stats.py: JellyseerrStatsProvider registered for the
  Jellyfin service; reuses one authenticated client per service (lru_cache) and
  caches the StatsResult for ~10s under a lock, so multiple widgets + the tab
  collapse onto one Jellyseerr fetch (same lesson as the qBittorrent client).
  Accepts jellyseerr_api_key from secrets OR config during the upcoming
  config->secret migration.
- Jellyfin service gains two widget kinds: `stat` (a Literal selector over the
  six stats — the "extract one value into a widget" affordance) and
  `stats_overview` (all stats + recent list).
- widgets router routes widget_kind in {stat, stats_overview} to a generic
  StatsWidgetSource (dispatches to the service type's provider), independent of
  service type.
- new /api/jellyseerr/stats router endpoint for the Requests tab (resolves the
  Jellyfin service by id or first-enabled; shares the provider cache).

Tests: provider normalization, not-configured, TTL caching; stat selector +
overview + unknown-stat widget dispatch; 7 new tests. 400/400 backend pass;
ruff clean.

backend/tests/test_jellyseerr_stats.py

@@ -0,0 +1,117 @@
+"""Tests for the Jellyseerr stats provider + generic stat widget source."""
+
+from __future__ import annotations
+
+import asyncio
+from unittest.mock import MagicMock, patch
+
+from media_library_viewer_api.widgets.jellyseerr_stats import JellyseerrStatsProvider
+from media_library_viewer_api.widgets.sources import ServiceRecord, StatsWidgetSource
+from media_library_viewer_api.widgets.stats_provider import (
+    StatValue,
+    get_stats_provider,
+)
+
+
+def _service(
+    *,
+    jellyseerr_url: str = "https://js.example.com",
+    jellyseerr_api_key: str = "key",
+) -> ServiceRecord:
+    return ServiceRecord(
+        id="svc-jf",
+        service_type="jellyfin",
+        name="Jellyfin",
+        config={"jellyseerr_url": jellyseerr_url, "jellyseerr_api_key": jellyseerr_api_key},
+        secrets={},
+        enabled=True,
+    )
+
+
+_COUNTS = {"total": 5, "pending": 2, "approved": 1, "declined": 0, "processing": 1, "available": 1}
+_RECENT = [{"id": 1, "name": "Inception", "status": "pending", "media_status": "available"}]
+
+
+def test_provider_registered_for_jellyfin():
+    assert isinstance(get_stats_provider("jellyfin"), JellyseerrStatsProvider)
+
+
+def test_provider_returns_normalized_stats_and_recent():
+    provider = JellyseerrStatsProvider(ttl=0)
+    fake = MagicMock()
+    fake.request_count.return_value = _COUNTS
+    fake.recent_requests.return_value = _RECENT
+    with patch("media_library_viewer_api.widgets.jellyseerr_stats._jellyseer_client", return_value=fake):
+        result = provider.fetch_stats(_service())
+    assert [s.key for s in result.stats] == [
+        "total",
+        "pending",
+        "approved",
+        "declined",
+        "processing",
+        "available",
+    ]
+    by_key = {s.key: s.value for s in result.stats}
+    assert by_key["pending"] == 2 and by_key["total"] == 5
+    assert result.recent == _RECENT
+
+
+def test_provider_not_configured_returns_detail():
+    provider = JellyseerrStatsProvider()
+    result = provider.fetch_stats(_service(jellyseerr_url="", jellyseerr_api_key=""))
+    assert result.stats == []
+    assert "not configured" in (result.detail or "").lower()
+
+
+def test_provider_caches_within_ttl():
+    provider = JellyseerrStatsProvider(ttl=10)
+    fake = MagicMock()
+    fake.request_count.return_value = _COUNTS
+    fake.recent_requests.return_value = _RECENT
+    with patch("media_library_viewer_api.widgets.jellyseerr_stats._jellyseer_client", return_value=fake):
+        provider.fetch_stats(_service())
+        provider.fetch_stats(_service())  # served from cache
+    assert fake.request_count.call_count == 1
+
+
+def test_stat_widget_returns_selected_value():
+    src = StatsWidgetSource()
+    result = MagicMock()
+    result.detail = None
+    result.stats = [StatValue("total", "Total", 5), StatValue("pending", "Pending", 2)]
+    result.recent = []
+    provider = MagicMock()
+    provider.fetch_stats.return_value = result
+    with patch("media_library_viewer_api.widgets.sources.get_stats_provider", return_value=provider):
+        data = asyncio.run(src.fetch(_service(), "stat", {"stat": "pending"}))
+    assert data == {"key": "pending", "label": "Pending", "value": 2}
+
+
+def test_stats_overview_widget_returns_all_stats_and_recent():
+    src = StatsWidgetSource()
+    result = MagicMock()
+    result.detail = None
+    result.stats = [StatValue("total", "Total", 5), StatValue("pending", "Pending", 2)]
+    result.recent = _RECENT
+    provider = MagicMock()
+    provider.fetch_stats.return_value = result
+    with patch("media_library_viewer_api.widgets.sources.get_stats_provider", return_value=provider):
+        data = asyncio.run(src.fetch(_service(), "stats_overview", {}))
+    assert data["stats"] == [
+        {"key": "total", "label": "Total", "value": 5},
+        {"key": "pending", "label": "Pending", "value": 2},
+    ]
+    assert data["recent"] == _RECENT
+
+
+def test_stat_widget_unknown_stat_returns_error():
+    src = StatsWidgetSource()
+    result = MagicMock()
+    result.detail = None
+    result.stats = [StatValue("total", "Total", 5)]
+    result.recent = []
+    provider = MagicMock()
+    provider.fetch_stats.return_value = result
+    with patch("media_library_viewer_api.widgets.sources.get_stats_provider", return_value=provider):
+        data = asyncio.run(src.fetch(_service(), "stat", {"stat": "nope"}))
+    assert "error" in data

backend/tests/test_services.py

@@ -101,7 +101,12 @@ def test_authentik_service_definition():
 def test_definitions_declare_widget_kinds():
     assert {wk.kind for wk in get_service_definition("prometheus").widget_kinds} == {"metric", "chart", "gauge", "mean"}
     assert {wk.kind for wk in get_service_definition("alertmanager").widget_kinds} == {"active_alerts"}
-    assert {wk.kind for wk in get_service_definition("jellyfin").widget_kinds} == {"activity", "now_playing"}
+    assert {wk.kind for wk in get_service_definition("jellyfin").widget_kinds} == {
+        "activity",
+        "now_playing",
+        "stat",
+        "stats_overview",
+    }
     assert get_service_definition("nextcloud").widget_kinds == []
     assert get_service_definition("authentik").widget_kinds == []
     assert {wk.kind for wk in get_service_definition("backups").widget_kinds} == {"summary"}