Add project scaffold and SQLite storage layer
Bootstrap TypeScript/Hono/better-sqlite3/vitest project with multi-tenant
SqliteRepoStorage implementing @atproto/repo's RepoStorage interface.
- tsconfig.json, vitest.config.ts, .gitignore, README.md
- src/config.ts: env var parsing with validation
- src/db.ts: schema init for accounts, blocks, collections, blobs, firehose_events
- src/storage.ts: SqliteRepoStorage with account-scoped queries, transactional applyCommit, prev_data_cid tracking
- src/cbor-compat.ts: CBOR compat layer ported from cirrus
- src/index.ts: Hono health-check server
- test/storage.test.ts: 8 tests covering Repo.create, applyWrites, multi-tenant isolation, transaction atomicity