feat: add offline XboxUnity title autocomplete

[TrapEmAll]

Summary

• fixes the Library game-name column so missing names display as Unknown game instead of duplicating the TitleID
• adds a persistent XboxUnity title catalog with local name/TitleID search, ranking, source payloads, sync history, and stale-cache detection
• refreshes the full catalog in a background thread when missing or older than seven days
• adds an Add Games autocomplete popup showing game name, TitleID, and title type
• safely enriches only blank, unknown, or TitleID-shaped library names and preserves known/user-provided names
• adds manual UI and --sync-title-catalog refresh paths
• closes LibraryService SQLite handles immediately after queries
• documents the workflow and changelog entries

Migration

Schema migration 5 creates xboxunity_title_catalog and xboxunity_catalog_sync_runs. The migration is additive. Existing library rows are not rewritten unless their name is blank, unknown, or exactly equal to their TitleID.

XboxUnity transport

All XboxUnity requests remain explicitly HTTP-only. The catalog service rejects a non-HTTP XboxUnity base URL and tests enforce this constraint.

Validation

• 71 tests passed
• Ruff passed across the repository
• focused mypy check passed for title_catalog.py
• compileall and desktop import smoke checks passed
• live temporary-database sync completed all 52 pages and cached 5,159 titles
• local autocomplete returned Halo 3 - 4D5307E6 [360]

Notes

XboxUnity remains an independent service. The application stores returned metadata and source URLs locally, rate-limits catalog pagination, refreshes no more than weekly by default, and preserves the last usable cache if a refresh fails.