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/tower-control.mjs

@@ -0,0 +1,25 @@
+/**
+ * @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: "M18.2 12.27 20 6H4l1.8 6.27a1 1 0 0 0 .95.73h10.5a1 1 0 0 0 .96-.73Z", key: "1pledb" }
+  ],
+  ["path", { d: "M8 13v9", key: "hmv0ci" }],
+  ["path", { d: "M16 22v-9", key: "ylnf1u" }],
+  ["path", { d: "m9 6 1 7", key: "dpdgam" }],
+  ["path", { d: "m15 6-1 7", key: "ls7zgu" }],
+  ["path", { d: "M12 6V2", key: "1pj48d" }],
+  ["path", { d: "M13 2h-2", key: "mj6ths" }]
+];
+const TowerControl = createLucideIcon("tower-control", __iconNode);
+
+export { __iconNode, TowerControl as default };
+//# sourceMappingURL=tower-control.mjs.map