feat: add anime metadata editing and NFO diagnostics

- Add PUT /anime/{key} endpoint for updating anime key, tmdb_id, tvdb_id
- Add NFO diagnostics and repair endpoints (GET/POST /nfo/diagnostics)
- Add edit modal UI with context menu integration
- Add frontend JS modules for context-menu and edit-modal
- Add comprehensive tests for edit, rename, and NFO repair flows

src/server/models/nfo.py

@@ -355,3 +355,29 @@ class NFOMissingResponse(BaseModel):
         ...,
         description="List of series missing NFO"
     )
+
+
+class NfoDiagnosticsResponse(BaseModel):
+    """Response for NFO diagnostics 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")
+    missing_tags: List[str] = Field(
+        default_factory=list,
+        description="List of missing required tag names"
+    )
+    required_tags: List[str] = Field(
+        default_factory=list,
+        description="All required tag names for reference"
+    )
+
+
+class NfoRepairResponse(BaseModel):
+    """Response after NFO repair attempt."""
+
+    success: bool = Field(..., description="Whether repair succeeded")
+    message: str = Field(..., description="Human-readable result message")
+    repaired_tags: List[str] = Field(
+        default_factory=list,
+        description="Tags that were missing before repair"
+    )