Hyperdrive NeonDB + D1 Test Worker

Hyperdrive Endpoints:
- /test-connection - Test database connection
- /test-query - Test database query
- /query-tables - List all tables
- /query-shushu?limit=N - Query shushu book content
- /search-shushu?q=keyword&limit=N - Search shushu book
- /shushu-stats - Get shushu book statistics

D1 Endpoints:
- /d1-init - Initialize semaphore database
- /d1-test - Test D1 database
- GET /d1-users - Get all users
- POST /d1-users - Create new user