feat(anime): rename NFO Diagnostics to Anime Settings + add edit endpoints

Replaces the read-only 'NFO Diagnostics' page with a full per-anime
Settings page reached from the right-click context menu on series cards.
Users can now view and edit key, name, folder, tmdb_id, tvdb_id and site
for each anime; changes are persisted to the DB and optionally written
back to the NFO file or used to regenerate it.

Backend
- Rename NfoDiagnosticsResponse -> NfoSettingsResponse,
  NfoSeriesDiagnostics -> NfoSeriesSettings
- Rename get_nfo_diagnostics -> get_nfo_settings,
  repair_nfo -> repair_nfo_settings
- Fix nfo.py bug: repair was calling non-existent
  update_series_nfo_status(); now uses update_nfo_status() and an
  explicit AnimeSeriesService.update(nfo_path=...)
- New endpoints on /api/anime/{key}:
    GET  /settings            -> AnimeSettingsResponse
    PUT  /settings            -> AnimeSettingsResponse
                                 (body: name/folder/tmdb_id/tvdb_id/site,
                                  options: apply_to_nfo, rename_disk)
    POST /regenerate-nfo      -> AnimeSettingsRegenerateNfoResponse
- New Pydantic models: AnimeSettingsResponse,
  AnimeSettingsUpdateRequest, AnimeSettingsRegenerateNfoResponse
- /anime/settings page route; /settings/nfo now 301-redirects to it

Frontend
- New AniWorld.AnimeSettingsManager JS module (single-page form,
  no tabs) with public API init/loadSeries/saveSettings/regenerateNfo/
  validateField/populateForm/showSaveSuccess/showError
- New anime-settings.html template + anime-settings.css
- Right-click menu: data-action 'nfo-diagnostics' replaced by
  'anime-settings' (label 'Anime Settings'), navigates to
  /anime/settings?key=...
- Library 'Open NFO Diagnostics' link renamed to 'Open Anime Settings'

Bug fix
- context-menu click handler was calling hide() BEFORE building the
  navigation URL, which cleared currentSeriesKey to null and produced
  /anime/settings?key=null. Captures the key into a local const first.
  Regression-locked by tests/frontend/unit/context_menu.test.js.

Tests
- 21 new pytest tests in tests/api/test_anime_settings_endpoints.py
  (GET/PUT/regenerate-nfo, auth, validation, nfo-repair bug regression)
- tests/api/test_nfo_endpoints.py trimmed to 6 focused tests
- 31 new Vitest unit tests for AnimeSettingsManager
- 5 new Vitest unit tests for ContextMenu (incl. source-invariant
  regression guard for the hide()-before-key bug)
- 5 new Playwright E2E tests covering right-click, direct nav,
  legacy /settings/nfo redirect, and context-menu labels
- New vitest.config.js (environment: happy-dom)

Docs
- Docs/API.md: new section 'Anime Settings Endpoints'
- Docs/CHANGELOG.md: documents the rename and the context-menu bug fix

Verified
- pytest: 27/27 (21 new + 6 trimmed nfo)
- vitest: 36/36 (31 anime-settings + 5 context-menu)
- playwright e2e: 5/5

src/server/models/anime.py

@@ -196,7 +196,7 @@ class AnimeDetailsResponse(BaseModel):
 
 class TMDBSearchResult(BaseModel):
     """TMDB search result for auto-lookup functionality.
-    
+
     Attributes:
         tmdb_id: TMDB ID of the matched series
         title: Title from TMDB
@@ -210,3 +210,88 @@ class TMDBSearchResult(BaseModel):
     year: Optional[int] = Field(None, description="Release year")
     overview: Optional[str] = Field(None, description="Short description")
     vote_average: Optional[float] = Field(None, description="TMDB rating")
+
+
+class AnimeSettingsResponse(BaseModel):
+    """Response payload for the Anime Settings page.
+
+    Surfaces every anime_series field that can be viewed or edited
+    by the user. Used by GET /api/anime/{key}/settings and the
+    PUT response.
+    """
+
+    key: str = Field(..., description="Series unique key (primary identifier)")
+    name: str = Field(..., description="Series display name")
+    site: str = Field(..., description="Provider site URL")
+    folder: str = Field(..., description="Filesystem folder name")
+    year: Optional[int] = Field(None, description="Release year")
+    tmdb_id: Optional[int] = Field(None, description="TMDB ID")
+    tvdb_id: Optional[int] = Field(None, description="TVDB ID")
+    has_nfo: bool = Field(False, description="Whether tvshow.nfo exists")
+    nfo_path: Optional[str] = Field(None, description="Path to tvshow.nfo file")
+    nfo_created_at: Optional[str] = Field(None, description="ISO timestamp when NFO created")
+    nfo_updated_at: Optional[str] = Field(None, description="ISO timestamp when NFO updated")
+    loading_status: Optional[str] = Field(
+        None, description="Current loading status of the series"
+    )
+    episode_count: int = Field(0, description="Total number of episodes tracked")
+    missing_episode_count: int = Field(0, description="Number of missing episodes")
+
+
+class AnimeSettingsUpdateRequest(BaseModel):
+    """Request payload for PUT /api/anime/{key}/settings.
+
+    All fields are optional. Only the fields that are provided will
+    be updated. Field-level validation happens in the API endpoint
+    (e.g. folder sanitization, TMDB ID format).
+    """
+
+    name: Optional[str] = Field(
+        None,
+        min_length=1,
+        max_length=500,
+        description="Series display name",
+    )
+    folder: Optional[str] = Field(
+        None,
+        min_length=1,
+        max_length=1000,
+        description="Filesystem folder name",
+    )
+    tmdb_id: Optional[int] = Field(
+        None,
+        ge=1,
+        le=9999999999,
+        description="TMDB ID (positive integer, max 10 digits)",
+    )
+    tvdb_id: Optional[int] = Field(
+        None,
+        ge=1,
+        le=9999999999,
+        description="TVDB ID (positive integer, max 10 digits)",
+    )
+    site: Optional[str] = Field(
+        None,
+        max_length=500,
+        description="Provider site URL",
+    )
+    apply_to_nfo: bool = Field(
+        False,
+        description="If true, regenerate tvshow.nfo with the new values",
+    )
+    rename_disk: bool = Field(
+        False,
+        description="If true and folder changed, rename the folder on disk",
+    )
+
+
+class AnimeSettingsRegenerateNfoResponse(BaseModel):
+    """Response payload for POST /api/anime/{key}/regenerate-nfo."""
+
+    success: bool = Field(..., description="Whether regeneration succeeded")
+    message: str = Field(..., description="Human-readable result message")
+    nfo_path: Optional[str] = Field(None, description="Path to regenerated NFO file")
+    repaired_tags: List[str] = Field(
+        default_factory=list,
+        description="Tags that were missing before regeneration",
+    )

src/server/models/nfo.py

@@ -357,8 +357,8 @@ class NFOMissingResponse(BaseModel):
     )
 
 
-class NfoDiagnosticsResponse(BaseModel):
-    """Response for NFO diagnostics showing missing required tags."""
+class NfoSettingsResponse(BaseModel):
+    """Response for NFO settings inspection showing missing required tags."""
 
     has_nfo: bool = Field(..., description="Whether tvshow.nfo exists")
     nfo_path: Optional[str] = Field(None, description="Path to NFO file if exists")
@@ -372,8 +372,8 @@ class NfoDiagnosticsResponse(BaseModel):
     )
 
 
-class NfoSeriesDiagnostics(BaseModel):
-    """Diagnostics for a single series in the needs-repair list."""
+class NfoSeriesSettings(BaseModel):
+    """Settings summary for a single series in the needs-repair list."""
 
     key: str = Field(..., description="Series unique key")
     name: str = Field(..., description="Series display name")