[Docs] Correct the documented Redis port in the platform guide

## Location docs/platform.md, Services and Configuration sections ## Problem The platform guide documents Redis as port 6371 in the generated environment example and configuration table, while the Compose configuration uses Redis port 6379 by default. ## Correction Replace incorrect 6371 values with verified default 6379 where they refer to Redis. Distinguish host-published development ports from internal container ports if needed. ## Acceptance criteria - The platform guide consistently documents Redis default port 6379. - The example .env and configuration table agree with Compose. - No configuration or source code is changed.