feat(db): add core Drizzle schema tables (hardware, games, gameVersions)

- Create lib/db/schema/ directory with barrel export index.ts
- Add hardware table with device_type enum (handled/console)
- Add games table with Steam metadata, sync fields, and JSON genres
- Add game_versions table with composite unique (gameId, buildId) and cascade delete

Refs: Chunk 2 of database schema implementation

lib/db/schema/index.ts

@@ -0,0 +1,6 @@
+// Barrel export — will be populated as schema files are created
+export * from "./games"
+export * from "./gameVersions"
+export * from "./hardware"
+export * from "./performanceEntries"
+export * from "./gamePlatformSupport"