Reduce Logfire log noise for cleaner observability (#60)

- Remove explicit SQLAlchemy instrumentation from database.py
- Add uninstrument() call to prevent auto-instrumentation of pg_catalog queries
- Remove redundant "Starting..." and "...completed" info logs from Modal functions
- Keep useful early-return logs like "Simulation already completed"
- Clean up force_flush() placement in economy functions

Author: nikhilwoodruff

src/policyengine_api/main.py

@@ -35,6 +35,14 @@ def _scrubbing_callback(m: logfire.ScrubMatch):
     )
     logfire.instrument_httpx()
 
+    # Disable noisy SQLAlchemy auto-instrumentation
+    try:
+        from opentelemetry.instrumentation.sqlalchemy import SQLAlchemyInstrumentor
+
+        SQLAlchemyInstrumentor().uninstrument()
+    except ImportError:
+        pass  # Not installed
+
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):