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/chess-rook.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 = [
+  [
+    "path",
+    { d: "M5 20a2 2 0 0 1 2-2h10a2 2 0 0 1 2 2v1a1 1 0 0 1-1 1H6a1 1 0 0 1-1-1z", key: "b89hwq" }
+  ],
+  ["path", { d: "M10 2v2", key: "7u0qdc" }],
+  ["path", { d: "M14 2v2", key: "6buw04" }],
+  ["path", { d: "m17 18-1-9", key: "10nd7q" }],
+  ["path", { d: "M6 2v5a2 2 0 0 0 2 2h8a2 2 0 0 0 2-2V2", key: "uxf4yx" }],
+  ["path", { d: "M6 4h12", key: "1x2ag7" }],
+  ["path", { d: "m7 18 1-9", key: "1si9vq" }]
+];
+const ChessRook = createLucideIcon("chess-rook", __iconNode);
+
+export { __iconNode, ChessRook as default };
+//# sourceMappingURL=chess-rook.mjs.map