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/lib/config.ts

@@ -0,0 +1,60 @@
+/**
+ * Centralized API Configuration
+ *
+ * This module provides a single source of truth for all API endpoints and URLs.
+ * All components should import from here instead of reading environment variables directly.
+ *
+ * Environment Variables:
+ * - NEXT_PUBLIC_API_URL: The main API server URL (default: http://localhost:3001)
+ * - NEXT_PUBLIC_ORCHESTRATOR_URL: The orchestrator service URL (default: same as API URL)
+ */
+
+/**
+ * Default API server URL for local development
+ */
+const DEFAULT_API_URL = "http://localhost:3001";
+
+/**
+ * Main API server URL
+ * Used for authentication, tasks, events, knowledge, and all core API calls
+ */
+export const API_BASE_URL = process.env.NEXT_PUBLIC_API_URL ?? DEFAULT_API_URL;
+
+/**
+ * Orchestrator service URL
+ * Used for agent management, task progress, and orchestration features
+ * Falls back to main API URL if not specified (they may run on the same server)
+ */
+export const ORCHESTRATOR_URL = process.env.NEXT_PUBLIC_ORCHESTRATOR_URL ?? API_BASE_URL;
+
+/**
+ * Build a full API endpoint URL
+ * @param endpoint - The API endpoint path (should start with /)
+ * @returns The full URL for the endpoint
+ */
+export function buildApiUrl(endpoint: string): string {
+  return `${API_BASE_URL}${endpoint}`;
+}
+
+/**
+ * Build a full orchestrator endpoint URL
+ * @param endpoint - The orchestrator endpoint path (should start with /)
+ * @returns The full URL for the endpoint
+ */
+export function buildOrchestratorUrl(endpoint: string): string {
+  return `${ORCHESTRATOR_URL}${endpoint}`;
+}
+
+/**
+ * Configuration object for convenient access to all URLs
+ */
+export const apiConfig = {
+  /** Main API base URL */
+  baseUrl: API_BASE_URL,
+  /** Orchestrator service URL */
+  orchestratorUrl: ORCHESTRATOR_URL,
+  /** Build full API URL for an endpoint */
+  buildUrl: buildApiUrl,
+  /** Build full orchestrator URL for an endpoint */
+  buildOrchestratorUrl,
+} as const;