feat: add NfoRepairService for missing NFO tag detection

docs/ARCHITECTURE.md

@@ -207,6 +207,8 @@ src/core/
 |   +-- nfo_models.py       # Pydantic models for tvshow.nfo (TVShowNFO, ActorInfo…)
 +-- services/               # Domain services
 |   +-- nfo_service.py      # NFO lifecycle: create / update tvshow.nfo
+|   +-- nfo_repair_service.py # Detect & repair incomplete tvshow.nfo files
+|   |                       #   (parse_nfo_tags, find_missing_tags, NfoRepairService)
 |   +-- tmdb_client.py      # Async TMDB API client
 +-- utils/                  # Utility helpers (no side-effects)
 |   +-- nfo_generator.py    # TVShowNFO → XML serialiser

docs/CHANGELOG.md

@@ -51,6 +51,10 @@ This changelog follows [Keep a Changelog](https://keepachangelog.com/) principle
   500 lines and isolate pure mapping logic.
 - **US MPAA rating**: `_extract_rating_by_country(ratings, "US")` now maps the
   US TMDB content rating to the `<mpaa>` NFO tag.
+- **`NfoRepairService` (`src/core/services/nfo_repair_service.py`)**: New service
+  that detects incomplete `tvshow.nfo` files and triggers TMDB re-fetch.
+  Provides `parse_nfo_tags()`, `find_missing_tags()`, `nfo_needs_repair()`, and
+  `NfoRepairService.repair_series()`.  13 required tags are checked.
 
 ### Changed