Fix "server closed connection unexpectedly" db issue

The engine outlives individual requests, so pooled connections can be
dropped server-side (idle timeouts, firewall reaps, failovers) while
still sitting in the pool. pool_pre_ping validates a connection before
use and transparently reconnects if it is dead; pool_recycle bounds
connection age so they are refreshed before common idle-timeout windows.
Without these, a stale connection surfaces as "server closed the
connection unexpectedly".

Assisted-by: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: Lukas Puehringer <lukas.puehringer@eclipse-foundation.org>

Author: lukpueh

pia/main.py

@@ -38,7 +38,11 @@
 @asynccontextmanager
 async def lifespan(app: FastAPI):
     """Initialize database engine and session factory on app startup."""
-    engine = create_engine(settings.database_url)
+    engine = create_engine(
+        settings.database_url,
+        pool_pre_ping=True,
+        pool_recycle=1800,
+    )
     app.state.session_factory = sessionmaker(bind=engine)
     logger.info("Database engine and session factory initialized")
     yield