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/backpack.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: "M4 10a4 4 0 0 1 4-4h8a4 4 0 0 1 4 4v10a2 2 0 0 1-2 2H6a2 2 0 0 1-2-2z", key: "1ol0lm" }
+  ],
+  ["path", { d: "M8 10h8", key: "c7uz4u" }],
+  ["path", { d: "M8 18h8", key: "1no2b1" }],
+  ["path", { d: "M8 22v-6a2 2 0 0 1 2-2h4a2 2 0 0 1 2 2v6", key: "1fr6do" }],
+  ["path", { d: "M9 6V4a2 2 0 0 1 2-2h2a2 2 0 0 1 2 2v2", key: "donm21" }]
+];
+const Backpack = createLucideIcon("backpack", __iconNode);
+
+export { __iconNode, Backpack as default };
+//# sourceMappingURL=backpack.mjs.map