chore: remove unused redis service from docker-compose

[Devadakene]

Closes #480

Description

This PR removes the unused redis service from the docker-compose.yml configuration. Currently, the application codebase relies on in-memory Maps and does not connect to Redis, making the redis container unnecessary dead infrastructure.

Specifically, this PR:

• Removes the redis service and redis_data volume from docker-compose.yml.
• Removes the hard depends_on: service_healthy condition and the REDIS_URL environment variable from the backend service.
• Removes the Redis resource allocation tests from src/__tests__/container-resources.test.ts.

These changes prevent wasted memory/CPU reservations and remove an unnecessary single point of failure that prevented the backend from starting.

Type of change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Chore (Optimization / Cleanup)

Testing checklist

• Tests pass locally
• Added new tests (if applicable)
• Code follows project conventions

Related issues

• Relates to the upcoming "Add Redis caching layer" feature (cleans up prematurely staged infrastructure).

Screenshots (if applicable)

N/A

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You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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