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/file-up.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: "M6 22a2 2 0 0 1-2-2V4a2 2 0 0 1 2-2h8a2.4 2.4 0 0 1 1.704.706l3.588 3.588A2.4 2.4 0 0 1 20 8v12a2 2 0 0 1-2 2z",
+      key: "1oefj6"
+    }
+  ],
+  ["path", { d: "M14 2v5a1 1 0 0 0 1 1h5", key: "wfsgrz" }],
+  ["path", { d: "M12 12v6", key: "3ahymv" }],
+  ["path", { d: "m15 15-3-3-3 3", key: "15xj92" }]
+];
+const FileUp = createLucideIcon("file-up", __iconNode);
+
+export { __iconNode, FileUp as default };
+//# sourceMappingURL=file-up.mjs.map