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/siren.mjs

@@ -0,0 +1,26 @@
+/**
+ * @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: "M7 18v-6a5 5 0 1 1 10 0v6", key: "pcx96s" }],
+  [
+    "path",
+    { d: "M5 21a1 1 0 0 0 1 1h12a1 1 0 0 0 1-1v-1a2 2 0 0 0-2-2H7a2 2 0 0 0-2 2z", key: "1b4s83" }
+  ],
+  ["path", { d: "M21 12h1", key: "jtio3y" }],
+  ["path", { d: "M18.5 4.5 18 5", key: "g5sp9y" }],
+  ["path", { d: "M2 12h1", key: "1uaihz" }],
+  ["path", { d: "M12 2v1", key: "11qlp1" }],
+  ["path", { d: "m4.929 4.929.707.707", key: "1i51kw" }],
+  ["path", { d: "M12 12v6", key: "3ahymv" }]
+];
+const Siren = createLucideIcon("siren", __iconNode);
+
+export { __iconNode, Siren as default };
+//# sourceMappingURL=siren.mjs.map