Added database repository layer with DatabaseService, 16 repositories, and tests

Database facade and repositories — Added a DatabaseService facade and a lazy `db` singleton that expose 16 fully typed repository classes covering every table in the SuprLogs schema (projects, commits, changelog entries, prompts, entitlements, subscribers, audit, etc.).
Comprehensive tests and type safety — Added 136 Vitest unit tests (all passing) and hand-written TypeScript types for the full schema; TypeScript compiled with zero errors.

Added DatabaseService and a lazy `db` singleton that instantiate and expose repository classes for every table.database
Implemented 16 repositories with explicit input/output interfaces and business methods (entry publish/approve/reject, prompt versioning, entitlement resolution, subscriber workflows, audit logs, etc.).backend

Added createDatabaseClient() factory to create a service-role Supabase client (server-only; requires SUPABASE_URL and SUPABASE_SERVICE_KEY).backend

Added 16 Vitest test files with 136 unit tests covering each repository; all tests passed and package TypeScript typecheck produced no errors.devops
Updated packages/database/package.json with test scripts and devDependencies for vitest and @vitest/ui.devops

Added a hand-written src/types.ts that defines the full Database type (Row/Insert/Update/Relationships) for all 19 tables and referenced the schema docs.database
Updated changelog and documentation references to include the new repository layer and schema details.