feat(frontend): add API client, layout, and routing

- Create Axios-based API client with sources, jobs, and dashboard endpoints
- Add responsive Layout component with navigation sidebar
- Set up React Router with Dashboard, Backups, and Settings routes
- Configure TanStack Query provider with default options
- Use lucide-react for navigation icons

frontend/node_modules/iconv-lite/lib/index.d.ts

@@ -0,0 +1,41 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License.
+ *  REQUIREMENT: This definition is dependent on the @types/node definition.
+ *  Install with `npm install @types/node --save-dev`
+ *--------------------------------------------------------------------------------------------*/
+
+declare module 'iconv-lite' {
+	// Basic API
+	export function decode(buffer: Buffer, encoding: string, options?: Options): string;
+
+	export function encode(content: string, encoding: string, options?: Options): Buffer;
+
+	export function encodingExists(encoding: string): boolean;
+
+	// Stream API
+	export function decodeStream(encoding: string, options?: Options): NodeJS.ReadWriteStream;
+
+	export function encodeStream(encoding: string, options?: Options): NodeJS.ReadWriteStream;
+
+	// Low-level stream APIs
+	export function getEncoder(encoding: string, options?: Options): EncoderStream;
+
+	export function getDecoder(encoding: string, options?: Options): DecoderStream;
+}
+
+export interface Options {
+    stripBOM?: boolean;
+    addBOM?: boolean;
+    defaultEncoding?: string;
+}
+
+export interface EncoderStream {
+	write(str: string): Buffer;
+	end(): Buffer | undefined;
+}
+
+export interface DecoderStream {
+	write(buf: Buffer): string;
+	end(): string | undefined;
+}