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/mail-plus.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 = [
+  ["path", { d: "M22 13V6a2 2 0 0 0-2-2H4a2 2 0 0 0-2 2v12c0 1.1.9 2 2 2h8", key: "12jkf8" }],
+  ["path", { d: "m22 7-8.97 5.7a1.94 1.94 0 0 1-2.06 0L2 7", key: "1ocrg3" }],
+  ["path", { d: "M19 16v6", key: "tddt3s" }],
+  ["path", { d: "M16 19h6", key: "xwg31i" }]
+];
+const MailPlus = createLucideIcon("mail-plus", __iconNode);
+
+export { __iconNode, MailPlus as default };
+//# sourceMappingURL=mail-plus.mjs.map