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/container.mjs

@@ -0,0 +1,26 @@
+/**
+ * @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: "M22 7.7c0-.6-.4-1.2-.8-1.5l-6.3-3.9a1.72 1.72 0 0 0-1.7 0l-10.3 6c-.5.2-.9.8-.9 1.4v6.6c0 .5.4 1.2.8 1.5l6.3 3.9a1.72 1.72 0 0 0 1.7 0l10.3-6c.5-.3.9-1 .9-1.5Z",
+      key: "1t2lqe"
+    }
+  ],
+  ["path", { d: "M10 21.9V14L2.1 9.1", key: "o7czzq" }],
+  ["path", { d: "m10 14 11.9-6.9", key: "zm5e20" }],
+  ["path", { d: "M14 19.8v-8.1", key: "159ecu" }],
+  ["path", { d: "M18 17.5V9.4", key: "11uown" }]
+];
+const Container = createLucideIcon("container", __iconNode);
+
+export { __iconNode, Container as default };
+//# sourceMappingURL=container.mjs.map