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/thermometer-snowflake.mjs

@@ -0,0 +1,23 @@
+/**
+ * @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: "m10 20-1.25-2.5L6 18", key: "18frcb" }],
+  ["path", { d: "M10 4 8.75 6.5 6 6", key: "7mghy3" }],
+  ["path", { d: "M10.585 15H10", key: "4nqulp" }],
+  ["path", { d: "M2 12h6.5L10 9", key: "kv9z4n" }],
+  ["path", { d: "M20 14.54a4 4 0 1 1-4 0V4a2 2 0 0 1 4 0z", key: "yu0u2z" }],
+  ["path", { d: "m4 10 1.5 2L4 14", key: "k9enpj" }],
+  ["path", { d: "m7 21 3-6-1.5-3", key: "j8hb9u" }],
+  ["path", { d: "m7 3 3 6h2", key: "1bbqgq" }]
+];
+const ThermometerSnowflake = createLucideIcon("thermometer-snowflake", __iconNode);
+
+export { __iconNode, ThermometerSnowflake as default };
+//# sourceMappingURL=thermometer-snowflake.mjs.map