refactor: remove Edit Metadata right-click option

Removes the Edit Metadata feature from the anime context menu and
deletes all related backend/frontend code:

Backend:
- DELETE PUT /api/anime/{anime_key} endpoint
- DELETE AnimeMetadataUpdate model and KEY_PATTERN regex
- DELETE MAX_INPUT_LENGTH constant

Frontend:
- DELETE edit-modal.js component
- DELETE edit metadata modal HTML from index.html
- DELETE edit-modal.js script tag
- DELETE edit-only CSS (.edit-modal-content, .edit-section,
  .field-error, .input-error, .key-warning, .info-grid,
  .info-item, .input-with-action, .btn-fetch-tmdb, .tmdb-*)
- REMOVE 'Edit Metadata' item from context menu (NFO Diagnostics
  preserved)

Tests:
- DELETE test_anime_edit_endpoints.py
- DELETE test_edit_modal.py
- DELETE test_anime_key_rename.py

src/server/api/anime.py

@@ -18,7 +18,6 @@ from src.server.exceptions import (
 )
 from src.server.models.anime import (
     AnimeDetailsResponse,
-    AnimeMetadataUpdate,
     TMDBSearchResult,
 )
 from src.server.services.anime_service import AnimeService, AnimeServiceError
@@ -1310,78 +1309,3 @@ async def search_tmdb_for_series(
     ]
 
 
-# Maximum allowed input size for security
-MAX_INPUT_LENGTH = 100000  # 100KB
-
-
-@router.put("/{anime_key}")
-async def update_anime_metadata(
-    anime_key: str,
-    body: AnimeMetadataUpdate,
-    _auth: dict = Depends(require_auth),
-    db: AsyncSession = Depends(get_database_session),
-) -> dict:
-    """Update anime metadata (key, tmdb_id, tvdb_id).
-
-    Args:
-        anime_key: Current series key to update
-        body: Fields to update (all optional)
-        _auth: Authentication dependency
-        db: Database session
-
-    Returns:
-        Updated series metadata
-
-    Raises:
-        HTTPException 404: Series not found
-        HTTPException 409: Key conflict (new key already exists)
-        HTTPException 422: Validation error
-    """
-    series = await AnimeSeriesService.get_by_key(db, anime_key)
-    if not series:
-        raise HTTPException(
-            status_code=status.HTTP_404_NOT_FOUND,
-            detail=f"Series with key '{anime_key}' not found",
-        )
-
-    updates = {}
-
-    if body.key is not None and body.key != anime_key:
-        existing = await AnimeSeriesService.get_by_key(db, body.key)
-        if existing:
-            raise HTTPException(
-                status_code=status.HTTP_409_CONFLICT,
-                detail=f"A series with key '{body.key}' already exists",
-            )
-        updates["key"] = body.key
-
-    if body.tmdb_id is not None:
-        updates["tmdb_id"] = body.tmdb_id
-
-    if body.tvdb_id is not None:
-        updates["tvdb_id"] = body.tvdb_id
-
-    if not updates:
-        return {
-            "key": series.key,
-            "tmdb_id": series.tmdb_id,
-            "tvdb_id": series.tvdb_id,
-            "message": "No changes",
-        }
-
-    updated = await AnimeSeriesService.update(db, series.id, **updates)
-    await db.commit()
-
-    logger.info(
-        "Updated metadata for '%s': %s",
-        anime_key,
-        updates,
-    )
-
-    return {
-        "key": updated.key,
-        "tmdb_id": updated.tmdb_id,
-        "tvdb_id": updated.tvdb_id,
-        "message": "Metadata updated successfully",
-    }
-