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/combine.mjs

@@ -0,0 +1,21 @@
+/**
+ * @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: "M14 3a1 1 0 0 1 1 1v5a1 1 0 0 1-1 1", key: "1l7d7l" }],
+  ["path", { d: "M19 3a1 1 0 0 1 1 1v5a1 1 0 0 1-1 1", key: "9955pe" }],
+  ["path", { d: "m7 15 3 3", key: "4hkfgk" }],
+  ["path", { d: "m7 21 3-3H5a2 2 0 0 1-2-2v-2", key: "1xljwe" }],
+  ["rect", { x: "14", y: "14", width: "7", height: "7", rx: "1", key: "1cdgtw" }],
+  ["rect", { x: "3", y: "3", width: "7", height: "7", rx: "1", key: "zi3rio" }]
+];
+const Combine = createLucideIcon("combine", __iconNode);
+
+export { __iconNode, Combine as default };
+//# sourceMappingURL=combine.mjs.map