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/captions-off.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: "M10.5 5H19a2 2 0 0 1 2 2v8.5", key: "jqtk4d" }],
+  ["path", { d: "M17 11h-.5", key: "1961ue" }],
+  ["path", { d: "M19 19H5a2 2 0 0 1-2-2V7a2 2 0 0 1 2-2", key: "1keqsi" }],
+  ["path", { d: "m2 2 20 20", key: "1ooewy" }],
+  ["path", { d: "M7 11h4", key: "1o1z6v" }],
+  ["path", { d: "M7 15h2.5", key: "1ina1g" }]
+];
+const CaptionsOff = createLucideIcon("captions-off", __iconNode);
+
+export { __iconNode, CaptionsOff as default };
+//# sourceMappingURL=captions-off.mjs.map