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/migrate_add_location_slots.py

@@ -0,0 +1,24 @@
+"""
+Migration: Add location_slots column to job_reservations table.
+Stores the full ordered slot list (including empty/unassigned slots) as JSON.
+Run once per database.
+"""
+import sqlite3
+import os
+
+DB_PATH = os.environ.get("DB_PATH", "/app/data/seismo_fleet.db")
+
+def run():
+    conn = sqlite3.connect(DB_PATH)
+    cursor = conn.cursor()
+    existing = [r[1] for r in cursor.execute("PRAGMA table_info(job_reservations)").fetchall()]
+    if "location_slots" not in existing:
+        cursor.execute("ALTER TABLE job_reservations ADD COLUMN location_slots TEXT")
+        conn.commit()
+        print("Added location_slots column to job_reservations.")
+    else:
+        print("location_slots column already exists, skipping.")
+    conn.close()
+
+if __name__ == "__main__":
+    run()