fix(databases): update default Redis version from 7 to 8 (#4224)

Update Redis default image from redis:7 to redis:8 in:
- packages/server/src/setup/redis-setup.ts (internal Redis setup)
- packages/server/src/services/ai.ts (AI service template examples)
- apps/dokploy/components/dashboard/project/add-database.tsx (UI default)

Redis 8 provides better performance according to benchmarks while
maintaining stability. Closes #4172.

apps/dokploy/components/dashboard/project/add-database.tsx

@@ -62,7 +62,7 @@ const dockerImageDefaultPlaceholder: Record<DbType, string> = {
 	mariadb: "mariadb:11",
 	mysql: "mysql:8",
 	postgres: "postgres:18",
-	redis: "redis:7",
+	redis: "redis:8",
 };
 
 const databasesUserDefaultPlaceholder: Record<