chore: remove unused NEXT_PUBLIC_CLIENT_ID/SECRET env vars

The OAuth flow uses grant_type=mobile with a server-issued grant
(app/api/auth/token/route.js); no client_id/client_secret is sent at
runtime. These vars were dead — removed from Dockerfile args/env,
docker-compose, nixpacks, and docs. Also silences the Coolify
'variable not set' build warnings.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -282,8 +282,6 @@ cp .env.example .env.local
 # 4. تنظیم متغیرهای محیطی
 # ویرایش .env.local:
 NEXT_PUBLIC_API_URL=http://localhost:8000
-NEXT_PUBLIC_CLIENT_ID=your_client_id
-NEXT_PUBLIC_CLIENT_SECRET=your_client_secret
 DEV_MODE=TRUE
 
 # 5. اجرای پروژه در حالت Development
@@ -696,8 +694,6 @@ export function Providers({ children }) {
 ```env
 # API Configuration
 NEXT_PUBLIC_API_URL=https://api.nobat724.com
-NEXT_PUBLIC_CLIENT_ID=your_client_id
-NEXT_PUBLIC_CLIENT_SECRET=your_client_secret
 
 # Development Mode (TRUE/FALSE)
 DEV_MODE=FALSE