feat(ui): sidebar rework + ratings & favourites data layer

[FivelSystems]

Summary

UI rework of the library sidebar plus the ratings & favourites data layer.

Sidebar redesign

• Status, Creators, and Categories are now compact overlay dropdowns (each with its own search and a summary of picked values) instead of long lists that pushed the panel around.
• New filters in the freed space: a star-rating control, an Only favourites toggle, and a dependency-relationship group (Standalone / Removable). Removable is enable-agnostic — a disabled package still exists in the library.
• "All Packages" became a Clear all action shown only when a filter is active.
• The library's total package count is centred beneath its name (no longer an inline badge shoving the title off-centre).

Ratings & Favourites (data layer)

• Rate a package 1–5 stars and mark it a favourite from the right-click menu, with instant visual feedback (the menu owns live state; handlers write explicit target values, optimistic update + rollback on error).
• Ratings/favourites are keyed by package family (creator.name), so every version shares them, and persist in the local SQLite user_metadata table.
• Fully wired through the search engine: rating:4, rating:>=3, favorite:true tokens now match live, with autocomplete suggestions (previously these tokens were inert).
• Backend: SetRating/SetFavorite repo methods, hydration onto packages in GetCachedPackages, exposed via App.SetPackageRating / App.SetPackageFavorite (bindings regenerated).
• Desktop-only for now — web has no persistence endpoint yet, so the menu row is hidden there rather than showing controls that silently can't save. The mobile/web entry point lands with the upcoming card redesign.

Testing

• go build ./..., go test ./..., go vet ./...
• npx tsc --noEmit clean; npx vitest run — all frontend tests pass (new coverage for rating/favourite matching, suggestions, and user_metadata upsert/clamp/case-insensitivity).

Notes

• Migrations remain append-only; user_metadata was already present.
• GlobalOverlays.tsx is pre-existing dead code (kept type-correct here); flagged for adopt-or-delete separately.