- Add configurable pool settings via environment variables:
DB_POOL_SIZE, DB_MAX_OVERFLOW, DB_POOL_TIMEOUT, DB_POOL_RECYCLE,
DB_POOL_PRE_PING (defaults: 5, 10, 30s, 1800s, true)
- Enable pool_pre_ping by default to detect and recycle stale connections
- Add dispose_engines() called during FastAPI lifespan shutdown to
release all connections back to the database
- Skip pool configuration for SQLite (uses file-lock, not connection pools)
- Apply changes to both servers/ and electron/ FastAPI instances
Fixes#453 (stale connections exhausting pool)
Fixes#454 (missing pool configuration)