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/ajv/dist/vocabularies/applicator/thenElse.js

@@ -0,0 +1,13 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+const util_1 = require("../../compile/util");
+const def = {
+    keyword: ["then", "else"],
+    schemaType: ["object", "boolean"],
+    code({ keyword, parentSchema, it }) {
+        if (parentSchema.if === undefined)
+            (0, util_1.checkStrictMode)(it, `"${keyword}" without "if" is ignored`);
+    },
+};
+exports.default = def;
+//# sourceMappingURL=thenElse.js.map