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/bitcoin.mjs

@@ -0,0 +1,22 @@
+/**
+ * @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: "M11.767 19.089c4.924.868 6.14-6.025 1.216-6.894m-1.216 6.894L5.86 18.047m5.908 1.042-.347 1.97m1.563-8.864c4.924.869 6.14-6.025 1.215-6.893m-1.215 6.893-3.94-.694m5.155-6.2L8.29 4.26m5.908 1.042.348-1.97M7.48 20.364l3.126-17.727",
+      key: "yr8idg"
+    }
+  ]
+];
+const Bitcoin = createLucideIcon("bitcoin", __iconNode);
+
+export { __iconNode, Bitcoin as default };
+//# sourceMappingURL=bitcoin.mjs.map