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/calculator.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 = [
+  ["rect", { width: "16", height: "20", x: "4", y: "2", rx: "2", key: "1nb95v" }],
+  ["line", { x1: "8", x2: "16", y1: "6", y2: "6", key: "x4nwl0" }],
+  ["line", { x1: "16", x2: "16", y1: "14", y2: "18", key: "wjye3r" }],
+  ["path", { d: "M16 10h.01", key: "1m94wz" }],
+  ["path", { d: "M12 10h.01", key: "1nrarc" }],
+  ["path", { d: "M8 10h.01", key: "19clt8" }],
+  ["path", { d: "M12 14h.01", key: "1etili" }],
+  ["path", { d: "M8 14h.01", key: "6423bh" }],
+  ["path", { d: "M12 18h.01", key: "mhygvu" }],
+  ["path", { d: "M8 18h.01", key: "lrp35t" }]
+];
+const Calculator = createLucideIcon("calculator", __iconNode);
+
+export { __iconNode, Calculator as default };
+//# sourceMappingURL=calculator.mjs.map