feat: add location_slots to job_reservations for full slot persistence and update version to 0.9.1

Fix: modems do not show as "missing" any more, cleans up the dashboard.

backend/models.py

@@ -482,6 +482,10 @@ class JobReservation(Base):
     quantity_needed = Column(Integer, nullable=True)  # e.g., 8 units
     estimated_units = Column(Integer, nullable=True)
 
+    # Full slot list as JSON: [{"location_name": "North Gate", "unit_id": null}, ...]
+    # Includes empty slots (no unit assigned yet). Filled slots are authoritative in JobReservationUnit.
+    location_slots = Column(Text, nullable=True)
+
     # Metadata
     notes = Column(Text, nullable=True)
     color = Column(String, default="#3B82F6")  # For calendar display (blue default)