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/lib/refs/json-schema-2020-12/index.ts

@@ -0,0 +1,30 @@
+import type Ajv from "../../core"
+import type {AnySchemaObject} from "../../types"
+import * as metaSchema from "./schema.json"
+import * as applicator from "./meta/applicator.json"
+import * as unevaluated from "./meta/unevaluated.json"
+import * as content from "./meta/content.json"
+import * as core from "./meta/core.json"
+import * as format from "./meta/format-annotation.json"
+import * as metadata from "./meta/meta-data.json"
+import * as validation from "./meta/validation.json"
+
+const META_SUPPORT_DATA = ["/properties"]
+
+export default function addMetaSchema2020(this: Ajv, $data?: boolean): Ajv {
+  ;[
+    metaSchema,
+    applicator,
+    unevaluated,
+    content,
+    core,
+    with$data(this, format),
+    metadata,
+    with$data(this, validation),
+  ].forEach((sch) => this.addMetaSchema(sch, undefined, false))
+  return this
+
+  function with$data(ajv: Ajv, sch: AnySchemaObject): AnySchemaObject {
+    return $data ? ajv.$dataMetaSchema(sch, META_SUPPORT_DATA) : sch
+  }
+}