Fix 500 on reservation edit after DB reinit (issue #883)

saveEndpoints was bound at module load via db.transaction(...). When the
demo-mode hourly reset (or a self-hoster's backup restore) closes the DB
connection and reinitialises it, the bound transaction still references
the now-closed connection — every subsequent reservation save with an
endpoints field throws "The database connection is not open", which the
client surfaces as "Internal server error".

Bind the transaction lazily on each call so it always runs against the
current connection.

server/src/services/reservationService.ts

@@ -61,16 +61,24 @@ function resolveDayIdFromTime(
   return row?.id ?? null;
 }
 
-const saveEndpoints = db.transaction((reservationId: number, endpoints: EndpointInput[]) => {
-  db.prepare('DELETE FROM reservation_endpoints WHERE reservation_id = ?').run(reservationId);
-  const insert = db.prepare(`
-    INSERT INTO reservation_endpoints (reservation_id, role, sequence, name, code, lat, lng, timezone, local_time, local_date)
-    VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
-  `);
-  endpoints.forEach((e, i) => {
-    insert.run(reservationId, e.role, e.sequence ?? i, e.name, e.code ?? null, e.lat, e.lng, e.timezone ?? null, e.local_time ?? null, e.local_date ?? null);
+function saveEndpoints(reservationId: number, endpoints: EndpointInput[]): void {
+  // Bind the transaction lazily on each call. Binding at module load time
+  // captures the DB connection that was open then, which becomes invalid
+  // after demo-reset / restore-from-backup closes and reinitialises the
+  // connection — every later endpoint save would throw
+  // "The database connection is not open".
+  const tx = db.transaction((rid: number, eps: EndpointInput[]) => {
+    db.prepare('DELETE FROM reservation_endpoints WHERE reservation_id = ?').run(rid);
+    const insert = db.prepare(`
+      INSERT INTO reservation_endpoints (reservation_id, role, sequence, name, code, lat, lng, timezone, local_time, local_date)
+      VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+    `);
+    eps.forEach((e, i) => {
+      insert.run(rid, e.role, e.sequence ?? i, e.name, e.code ?? null, e.lat, e.lng, e.timezone ?? null, e.local_time ?? null, e.local_date ?? null);
+    });
   });
-});
+  tx(reservationId, endpoints);
+}
 
 export function listReservations(tripId: string | number) {
   const reservations = db.prepare(`