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/server.mjs

@@ -0,0 +1,19 @@
+/**
+ * @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 = [
+  ["rect", { width: "20", height: "8", x: "2", y: "2", rx: "2", ry: "2", key: "ngkwjq" }],
+  ["rect", { width: "20", height: "8", x: "2", y: "14", rx: "2", ry: "2", key: "iecqi9" }],
+  ["line", { x1: "6", x2: "6.01", y1: "6", y2: "6", key: "16zg32" }],
+  ["line", { x1: "6", x2: "6.01", y1: "18", y2: "18", key: "nzw8ys" }]
+];
+const Server = createLucideIcon("server", __iconNode);
+
+export { __iconNode, Server as default };
+//# sourceMappingURL=server.mjs.map