feat(nfo): implement NFO diagnostics and repair

- Add NFO API endpoints: diagnostics, repair, validate, needs-repair
- Create /settings/nfo page with full NFO management UI
- Add NFO status section to edit modal with repair functionality
- Add anime details API for edit modal pre-fill data
- Fix auth test fixtures in test_nfo_diagnostics_repair.py

Implements NFO diagnostics when editing anime series via right-click menu.
Users can now check NFO status, see missing tags, and repair NFOs
directly from the edit modal or the dedicated NFO settings page.

src/server/controllers/page_controller.py

@@ -69,3 +69,13 @@ async def unresolved_page(request: Request):
         request,
         title="Resolve Series - Aniworld"
     )
+
+
+@router.get("/settings/nfo", response_class=HTMLResponse)
+async def nfo_settings_page(request: Request):
+    """Serve the NFO diagnostics and repair settings page."""
+    return render_template(
+        "nfo-settings.html",
+        request,
+        title="NFO Diagnostics - Aniworld"
+    )