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/route.ts

@@ -30,8 +30,10 @@ export async function GET(request: NextRequest) {
       }
     }
     const { searchParams } = new URL(request.url);
-    const page = parseInt(searchParams.get('page') || '1');
-    const limit = parseInt(searchParams.get('limit') || '50');
+    const pageRaw = parseInt(searchParams.get('page') || '1');
+    const limitRaw = parseInt(searchParams.get('limit') || '50');
+    const page = Number.isFinite(pageRaw) && pageRaw > 0 ? pageRaw : 1;
+    const limit = Number.isFinite(limitRaw) && limitRaw > 0 && limitRaw <= 200 ? limitRaw : 50;
     const category = searchParams.get('category');
     const featured = searchParams.get('featured');
     const published = searchParams.get('published');
@@ -145,6 +147,8 @@ export async function POST(request: NextRequest) {
         { status: 403 }
       );
     }
+    const authError = requireSessionAuth(request);
+    if (authError) return authError;
 
     const data = await request.json();