feat: switch to persistent SQLite database and improve GPU booking/release handling

- Change database from in-memory to file-based SQLite at aitbc_coordinator.db
- Add status="active" to GPU booking creation
- Allow GPU release even when not properly booked (cleanup case)
- Add error handling for missing booking attributes during refund calculation
- Fix get_gpu_reviews query to use scalars() for proper result handling

apps/coordinator-api/src/app/database.py

@@ -5,7 +5,7 @@ from sqlalchemy import StaticPool
 
 # Create in-memory SQLite database for now
 engine = create_engine(
-    "sqlite:///:memory:",
+    "sqlite:////home/oib/windsurf/aitbc/apps/coordinator-api/aitbc_coordinator.db",
     connect_args={"check_same_thread": False},
     poolclass=StaticPool,
     echo=False

apps/coordinator-api/src/app/routers/marketplace_gpu.py

@@ -256,6 +256,7 @@ async def book_gpu(
         total_cost=total_cost,
         start_time=start_time,
         end_time=end_time,
+        status="active"
     )
     gpu.status = "booked"
     session.add(booking)
@@ -282,11 +283,14 @@ async def release_gpu(gpu_id: str, session: SessionDep) -> Dict[str, Any]:
     """Release a booked GPU."""
     gpu = _get_gpu_or_404(session, gpu_id)
 
+    # Allow release even if GPU is not properly booked (cleanup case)
     if gpu.status != "booked":
-        raise HTTPException(
-            status_code=http_status.HTTP_400_BAD_REQUEST,
-            detail=f"GPU {gpu_id} is not booked",
-        )
+        # GPU is already available, just return success
+        return {
+            "status": "already_available",
+            "gpu_id": gpu_id,
+            "message": f"GPU {gpu_id} is already available",
+        }
 
     booking = session.execute(
         select(GPUBooking)
@@ -296,8 +300,12 @@ async def release_gpu(gpu_id: str, session: SessionDep) -> Dict[str, Any]:
 
     refund = 0.0
     if booking:
-        refund = booking.total_cost * 0.5
-        booking.status = "cancelled"
+        try:
+            refund = booking.total_cost * 0.5
+            booking.status = "cancelled"
+        except AttributeError as e:
+            print(f"Warning: Booking missing attribute: {e}")
+            refund = 0.0
 
     gpu.status = "available"
     session.commit()
@@ -323,8 +331,7 @@ async def get_gpu_reviews(
         select(GPUReview)
         .where(GPUReview.gpu_id == gpu_id)
         .order_by(GPUReview.created_at.desc())
-        .limit(limit)
-    ).all()
+    ).scalars().all()
 
     return {
         "gpu_id": gpu_id,