refactor: enhance security and performance in configuration and API routes

- Update Content Security Policy (CSP) in next.config.ts to avoid `unsafe-eval` in production, improving security against XSS attacks.
- Refactor API routes to enforce admin authentication and session validation, ensuring secure access to sensitive endpoints.
- Optimize analytics data retrieval by using database aggregation instead of loading all records into memory, improving performance and reducing memory usage.
- Implement session token creation and verification for better session management and security across the application.
- Enhance error handling and input validation in various API routes to ensure robustness and prevent potential issues.

app/api/projects/export/route.ts

@@ -1,8 +1,14 @@
-import { NextResponse } from 'next/server';
+import { NextRequest, NextResponse } from 'next/server';
 import { projectService } from '@/lib/prisma';
+import { requireSessionAuth } from '@/lib/auth';
 
-export async function GET() {
+export async function GET(request: NextRequest) {
   try {
+    const isAdminRequest = request.headers.get('x-admin-request') === 'true';
+    if (!isAdminRequest) return NextResponse.json({ error: 'Admin access required' }, { status: 403 });
+    const authError = requireSessionAuth(request);
+    if (authError) return authError;
+
     // Get all projects with full data
     const projectsResult = await projectService.getAllProjects();
     const projects = projectsResult.projects || projectsResult;