Add sync error logging, extend error flash, fix unload saves

- Log workforce sync errors to backend stdout so they appear in docker logs
- Extend error flash from 5s to 15s so errors are readable
- Replace sendBeacon (POST-only) with keepalive fetch (PUT) on unload —
  sendBeacon was hitting 404s on all three unload saves

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/node_modules/lucide-react/dist/esm/icons/calendar-x-2.mjs

@@ -0,0 +1,21 @@
+/**
+ * @license lucide-react v1.24.0 - ISC
+ *
+ * This source code is licensed under the ISC license.
+ * See the LICENSE file in the root directory of this source tree.
+ */
+
+import createLucideIcon from '../createLucideIcon.mjs';
+
+const __iconNode = [
+  ["path", { d: "M8 2v4", key: "1cmpym" }],
+  ["path", { d: "M16 2v4", key: "4m81vk" }],
+  ["path", { d: "M21 13V6a2 2 0 0 0-2-2H5a2 2 0 0 0-2 2v14a2 2 0 0 0 2 2h8", key: "3spt84" }],
+  ["path", { d: "M3 10h18", key: "8toen8" }],
+  ["path", { d: "m17 22 5-5", key: "1k6ppv" }],
+  ["path", { d: "m17 17 5 5", key: "p7ous7" }]
+];
+const CalendarX2 = createLucideIcon("calendar-x-2", __iconNode);
+
+export { __iconNode, CalendarX2 as default };
+//# sourceMappingURL=calendar-x-2.mjs.map