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/square-m.mjs

@@ -0,0 +1,23 @@
+/**
+ * @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 16V8.5a.5.5 0 0 1 .9-.3l2.7 3.599a.5.5 0 0 0 .8 0l2.7-3.6a.5.5 0 0 1 .9.3V16",
+      key: "1ywlsj"
+    }
+  ],
+  ["rect", { x: "3", y: "3", width: "18", height: "18", rx: "2", key: "h1oib" }]
+];
+const SquareM = createLucideIcon("square-m", __iconNode);
+
+export { __iconNode, SquareM as default };
+//# sourceMappingURL=square-m.mjs.map