fix: update version tags to v28 and temporarily disable cache for predictions

src/config/env.validation.ts

@@ -23,7 +23,7 @@ export const envSchema = z.object({
   DATABASE_URL: z.string().url(),
   // AI Engine
   AI_ENGINE_URL: z.string().url().default("http://localhost:8000"),
-  AI_ENGINE_MODE: z.enum(["v25", "dual", "v26"]).default("v25"),
+  AI_ENGINE_MODE: z.enum(["v28-pro-max", "dual"]).default("v28-pro-max"),
 
   // JWT
   JWT_SECRET: z.string().min(32),