feat: comprehensive security and architecture improvements

- Add Zod validation schemas with strong password requirements (12+ chars, complexity)
- Implement rate limiting for authentication endpoints (registration, password reset)
- Remove duplicate MetricCard component, consolidate to ui/metric-card.tsx
- Update README.md to use pnpm commands consistently
- Enhance authentication security with 12-round bcrypt hashing
- Add comprehensive input validation for all API endpoints
- Fix security vulnerabilities in user registration and password reset flows

🤖 Generated with [Claude Code](https://claude.ai/code)

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

app/api/dashboard/session/[id]/route.ts

@@ -26,10 +26,7 @@ export async function GET(
     });
 
     if (!prismaSession) {
-      return NextResponse.json(
-        { error: "Session not found" },
-        { status: 404 }
-      );
+      return NextResponse.json({ error: "Session not found" }, { status: 404 });
     }
 
     // Map Prisma session object to ChatSession type