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/save-check.mjs

@@ -0,0 +1,25 @@
+/**
+ * @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: "M12.5 21H5a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h10.2a2 2 0 0 1 1.4.6l3.8 3.8a2 2 0 0 1 .6 1.4v4.35",
+      key: "6jbevg"
+    }
+  ],
+  ["path", { d: "m16 19 2 2 4-4", key: "1b14m6" }],
+  ["path", { d: "M17 15.13V14a1 1 0 0 0-1-1H8a1 1 0 0 0-1 1v7", key: "1bzeol" }],
+  ["path", { d: "M7 3v4a1 1 0 0 0 1 1h7", key: "t51u73" }]
+];
+const SaveCheck = createLucideIcon("save-check", __iconNode);
+
+export { __iconNode, SaveCheck as default };
+//# sourceMappingURL=save-check.mjs.map