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/compile/codegen/code.d.ts

@@ -0,0 +1,40 @@
+export declare abstract class _CodeOrName {
+    abstract readonly str: string;
+    abstract readonly names: UsedNames;
+    abstract toString(): string;
+    abstract emptyStr(): boolean;
+}
+export declare const IDENTIFIER: RegExp;
+export declare class Name extends _CodeOrName {
+    readonly str: string;
+    constructor(s: string);
+    toString(): string;
+    emptyStr(): boolean;
+    get names(): UsedNames;
+}
+export declare class _Code extends _CodeOrName {
+    readonly _items: readonly CodeItem[];
+    private _str?;
+    private _names?;
+    constructor(code: string | readonly CodeItem[]);
+    toString(): string;
+    emptyStr(): boolean;
+    get str(): string;
+    get names(): UsedNames;
+}
+export type CodeItem = Name | string | number | boolean | null;
+export type UsedNames = Record<string, number | undefined>;
+export type Code = _Code | Name;
+export type SafeExpr = Code | number | boolean | null;
+export declare const nil: _Code;
+type CodeArg = SafeExpr | string | undefined;
+export declare function _(strs: TemplateStringsArray, ...args: CodeArg[]): _Code;
+export declare function str(strs: TemplateStringsArray, ...args: (CodeArg | string[])[]): _Code;
+export declare function addCodeArg(code: CodeItem[], arg: CodeArg | string[]): void;
+export declare function strConcat(c1: Code, c2: Code): Code;
+export declare function stringify(x: unknown): Code;
+export declare function safeStringify(x: unknown): string;
+export declare function getProperty(key: Code | string | number): Code;
+export declare function getEsmExportName(key: Code | string | number): Code;
+export declare function regexpCode(rx: RegExp): Code;
+export {};