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/brush-cleaning.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: "m16 22-1-4", key: "1ow2iv" }],
+  [
+    "path",
+    {
+      d: "M19 14a1 1 0 0 0 1-1v-1a2 2 0 0 0-2-2h-3a1 1 0 0 1-1-1V4a2 2 0 0 0-4 0v5a1 1 0 0 1-1 1H6a2 2 0 0 0-2 2v1a1 1 0 0 0 1 1",
+      key: "11gii7"
+    }
+  ],
+  ["path", { d: "M19 14H5l-1.973 6.767A1 1 0 0 0 4 22h16a1 1 0 0 0 .973-1.233z", key: "bju7h4" }],
+  ["path", { d: "m8 22 1-4", key: "s3unb" }]
+];
+const BrushCleaning = createLucideIcon("brush-cleaning", __iconNode);
+
+export { __iconNode, BrushCleaning as default };
+//# sourceMappingURL=brush-cleaning.mjs.map