Add FTS-backed search (songs/albums/artists) and DB migration

[theovilardo]

Motivation

• Replace costly LIKE '%query%' full-table scans with an indexed full-text search to reduce CPU and latency for searches, following the optimization plan in OPTIM.md.
• Provide prefix matching and tokenization suitable for multilingual metadata to improve perceived responsiveness on large libraries.
• Ensure a seamless upgrade path by adding a database migration that builds the FTS tables and keeps schema versioning consistent.

Description

• Add Room FTS entities (SongFtsEntity, AlbumFtsEntity, ArtistFtsEntity) in SearchFtsEntities.kt to model FTS tables for songs, albums and artists.
• Bump database version to 12 and add MIGRATION_11_12 in PixelPlayDatabase.kt which creates songs_fts, albums_fts, and artists_fts virtual tables and triggers a rebuild.
• Replace LIKE queries with FTS MATCH queries in MusicDao.kt and join the base tables with the FTS virtual tables for search results.
• Update MusicRepositoryImpl.kt to build safe prefix FTS queries via buildFtsQuery(rawQuery) and pass the generated FTS query to the DAO, and register the new migration in AppModule.kt.

Testing

• No automated tests or builds were executed as part of this change.

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[chatgpt-codex-connector]

Add FTS sync triggers for migrated databases

The migration creates external-content FTS tables (content='songs', etc.) but does not create any triggers or other update path to keep the FTS index in sync after the one-time rebuild. For users upgrading from v11, any subsequent inserts/updates/deletes to songs/albums/artists will not update the FTS tables, so search results will silently miss new or modified items. To avoid stale search results, add the standard FTS4 content-table triggers in this migration (or switch to a Room migration that generates them).

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