fix(#338): Standardize API base URL and auth mechanism across components

- Create centralized config module (apps/web/src/lib/config.ts) exporting:
  - API_BASE_URL: Main API server URL from NEXT_PUBLIC_API_URL
  - ORCHESTRATOR_URL: Orchestrator service URL from NEXT_PUBLIC_ORCHESTRATOR_URL
  - Helper functions for building full URLs
- Update client.ts to import from central config
- Update LoginButton.tsx to use API_BASE_URL from config
- Update useWebSocket.ts to use API_BASE_URL from config
- Update AgentStatusWidget.tsx to use ORCHESTRATOR_URL from config
- Update TaskProgressWidget.tsx to use ORCHESTRATOR_URL from config
- Update useGraphData.ts to use API_BASE_URL from config
  - Fixed wrong default port (was 8000, now uses correct 3001)
- Add comprehensive tests for config module
- Update useWebSocket tests to properly mock config module

Refs #338

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/web/src/hooks/useWebSocket.ts

@@ -1,6 +1,7 @@
 import { useEffect, useState } from "react";
 import type { Socket } from "socket.io-client";
 import { io } from "socket.io-client";
+import { API_BASE_URL } from "@/lib/config";
 
 interface Task {
   id: string;
@@ -87,8 +88,8 @@ export function useWebSocket(
   } = callbacks;
 
   useEffect(() => {
-    // Get WebSocket URL from environment or default to API URL
-    const wsUrl = process.env.NEXT_PUBLIC_API_URL ?? "http://localhost:3001";
+    // Use WebSocket URL from central config
+    const wsUrl = API_BASE_URL;
 
     // Validate WebSocket security - warn if using insecure connection in production
     validateWebSocketSecurity(wsUrl);