docs: update .env.example with frontend configuration variables

- Add `API_BASE_URL`, `PORT`, and `ORIGIN` for frontend setup
- Group and organize settings for improved clarity

Author: Pdzly

.env.example

@@ -44,3 +44,8 @@ APP_SAVE_IP_ADDRESS=false
 
 # Optional: Rate limit bypass token for trusted apps
 # APP_BYPASS_TOKEN=your_secret_bypass_token_here
+
+# Frontend configurations
+API_BASE_URL=http://devbin:8000
+PORT=3000
+ORIGIN=http://localhost:3000