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/ajv.d.ts

@@ -0,0 +1,18 @@
+import type { AnySchemaObject } from "./types";
+import AjvCore from "./core";
+export declare class Ajv extends AjvCore {
+    _addVocabularies(): void;
+    _addDefaultMetaSchema(): void;
+    defaultMeta(): string | AnySchemaObject | undefined;
+}
+export default Ajv;
+export { Format, FormatDefinition, AsyncFormatDefinition, KeywordDefinition, KeywordErrorDefinition, CodeKeywordDefinition, MacroKeywordDefinition, FuncKeywordDefinition, Vocabulary, Schema, SchemaObject, AnySchemaObject, AsyncSchema, AnySchema, ValidateFunction, AsyncValidateFunction, SchemaValidateFunction, ErrorObject, ErrorNoParams, } from "./types";
+export { Plugin, Options, CodeOptions, InstanceOptions, Logger, ErrorsTextOptions } from "./core";
+export { SchemaCxt, SchemaObjCxt } from "./compile";
+export { KeywordCxt } from "./compile/validate";
+export { DefinedError } from "./vocabularies/errors";
+export { JSONType } from "./compile/rules";
+export { JSONSchemaType } from "./types/json-schema";
+export { _, str, stringify, nil, Name, Code, CodeGen, CodeGenOptions } from "./compile/codegen";
+export { default as ValidationError } from "./runtime/validation_error";
+export { default as MissingRefError } from "./compile/ref_error";