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/refs/json-schema-2019-09/index.js

@@ -0,0 +1,28 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+const metaSchema = require("./schema.json");
+const applicator = require("./meta/applicator.json");
+const content = require("./meta/content.json");
+const core = require("./meta/core.json");
+const format = require("./meta/format.json");
+const metadata = require("./meta/meta-data.json");
+const validation = require("./meta/validation.json");
+const META_SUPPORT_DATA = ["/properties"];
+function addMetaSchema2019($data) {
+    ;
+    [
+        metaSchema,
+        applicator,
+        content,
+        core,
+        with$data(this, format),
+        metadata,
+        with$data(this, validation),
+    ].forEach((sch) => this.addMetaSchema(sch, undefined, false));
+    return this;
+    function with$data(ajv, sch) {
+        return $data ? ajv.$dataMetaSchema(sch, META_SUPPORT_DATA) : sch;
+    }
+}
+exports.default = addMetaSchema2019;
+//# sourceMappingURL=index.js.map