feat: checkbox batch trip delete on the Pi (local-only)

- Pi history page gets a select checkbox column + 'Delete selected' button
  (mirrors the server UI)
- POST /api/trips/delete batch endpoint
- app_sql.delete_trips_batch() + deleted_trip_markers table so a later trip
  rebuild can't resurrect locally-deleted trips
- Deletion is local-only: raw tracking rows are kept and the remote server
  is never notified (it keeps its archival copy recomputed from uploaded rows)

tests/test_trip_sql.py

@@ -76,6 +76,36 @@ class TripSqlTest(unittest.TestCase):
 
         self.assertEqual(rebuilt[0], original[0])
 
+    def test_deleted_trip_is_not_resurrected_by_rebuild(self):
+        started = datetime(2026, 1, 1, 8)
+        self.insert_motion(1, 160, started, 45.5)
+        self.insert_motion(161, 10, started + timedelta(minutes=30), 45.6)
+        app_sql.refresh_trips(force=True)
+        self.assertEqual(
+            self.conn.execute("SELECT COUNT(*) FROM trips").fetchone()[0], 2
+        )
+
+        trip_ids = [
+            row[0]
+            for row in self.conn.execute("SELECT id FROM trips ORDER BY id").fetchall()
+        ]
+        self.assertEqual(app_sql.delete_trips_batch(trip_ids), 2)
+        self.assertEqual(
+            self.conn.execute("SELECT COUNT(*) FROM trips").fetchone()[0], 0
+        )
+        self.assertEqual(
+            self.conn.execute(
+                "SELECT COUNT(*) FROM deleted_trip_markers"
+            ).fetchone()[0],
+            2,
+        )
+
+        # A full rebuild must not resurrect locally-deleted trips.
+        app_sql.refresh_trips(force=True)
+        self.assertEqual(
+            self.conn.execute("SELECT COUNT(*) FROM trips").fetchone()[0], 0
+        )
+
 
 if __name__ == "__main__":
     unittest.main()