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/languages.mjs

@@ -0,0 +1,21 @@
+/**
+ * @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: "m5 8 6 6", key: "1wu5hv" }],
+  ["path", { d: "m4 14 6-6 2-3", key: "1k1g8d" }],
+  ["path", { d: "M2 5h12", key: "or177f" }],
+  ["path", { d: "M7 2h1", key: "1t2jsx" }],
+  ["path", { d: "m22 22-5-10-5 10", key: "don7ne" }],
+  ["path", { d: "M14 18h6", key: "1m8k6r" }]
+];
+const Languages = createLucideIcon("languages", __iconNode);
+
+export { __iconNode, Languages as default };
+//# sourceMappingURL=languages.mjs.map