feat: enhance environment configuration and CORS handling

- Added `NEXT_PUBLIC_APP_URL` and `NEXT_PUBLIC_CONTACT_EMAIL` to environment variables for frontend configuration.
- Updated CORS logic to support domain-based restrictions with dynamic origin validation.
- Improved frontend image hostname resolution using environment-driven URLs.
- Standardized contact email usage across the application.

frontend/src/app/(dashboard)/help/page.tsx

@@ -63,7 +63,9 @@ export default function HelpPage() {
 				<p className="text-muted-foreground">
 					N'hésitez pas à nous contacter sur nos réseaux sociaux ou par email.
 				</p>
-				<p className="font-semibold text-primary">contact@memegoat.fr</p>
+				<p className="font-semibold text-primary">
+					{process.env.NEXT_PUBLIC_CONTACT_EMAIL || "contact@memegoat.fr"}
+				</p>
 			</div>
 		</div>
 	);