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/check-line.mjs

@@ -0,0 +1,18 @@
+/**
+ * @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: "M20 4L9 15", key: "1qkx8z" }],
+  ["path", { d: "M21 19L3 19", key: "100sma" }],
+  ["path", { d: "M9 15L4 10", key: "9zxff7" }]
+];
+const CheckLine = createLucideIcon("check-line", __iconNode);
+
+export { __iconNode, CheckLine as default };
+//# sourceMappingURL=check-line.mjs.map