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/tree-deciduous.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 19a4 4 0 0 1-2.24-7.32A3.5 3.5 0 0 1 9 6.03V6a3 3 0 1 1 6 0v.04a3.5 3.5 0 0 1 3.24 5.65A4 4 0 0 1 16 19Z",
+      key: "oadzkq"
+    }
+  ],
+  ["path", { d: "M12 19v3", key: "npa21l" }]
+];
+const TreeDeciduous = createLucideIcon("tree-deciduous", __iconNode);
+
+export { __iconNode, TreeDeciduous as default };
+//# sourceMappingURL=tree-deciduous.mjs.map