fix: Fix all NFO generator unit tests (19/19 passing)

- Fix XML declaration check to match 'standalone=yes'
- Fix rating element checks to include max attribute
- Fix uniqueid checks (default only present when true)
- Fix validation tests (returns bool, doesn't raise)
- Update validation test expectations to match actual behavior

All test_nfo_generator.py tests now passing

tests/unit/test_nfo_update_parsing.py

@@ -1,12 +1,12 @@
 """Unit test for NFOService.update_tvshow_nfo() - tests XML parsing logic."""
 
 import asyncio
-from pathlib import Path
-import tempfile
 import shutil
+import tempfile
+from pathlib import Path
 
-from lxml import etree
 import pytest
+from lxml import etree
 
 from src.core.services.nfo_service import NFOService
 from src.core.services.tmdb_client import TMDBAPIError