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/message-square-lock.mjs

@@ -0,0 +1,24 @@
+/**
+ * @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: "M22 8.5V5a2 2 0 0 0-2-2H4a2 2 0 0 0-2 2v16.286a.71.71 0 0 0 1.212.502l2.202-2.202A2 2 0 0 1 6.828 19H10",
+      key: "fu6chl"
+    }
+  ],
+  ["path", { d: "M20 15v-2a2 2 0 0 0-4 0v2", key: "vl8a78" }],
+  ["rect", { x: "14", y: "15", width: "8", height: "5", rx: "1", key: "37aafw" }]
+];
+const MessageSquareLock = createLucideIcon("message-square-lock", __iconNode);
+
+export { __iconNode, MessageSquareLock as default };
+//# sourceMappingURL=message-square-lock.mjs.map