feat: extended Redis TLS and MinIO credential support

[aron-muon]

Summary

Adds Helm template flexibility and S3-compatible credential support to unblock deployments with self-signed CAs and non-standard secret key names (e.g. RustFS operator).

• Add extraVolumes / extraVolumeMounts to the deployment template, enabling users to mount additional volumes such as CA certificates for Redis TLS or S3/MinIO TLS verification
• Add env support to the deployment template, enabling individual env var injection with valueFrom references for mapping secret keys to different env var names
• Accept AWS_ACCESS_KEY_ID / AWS_SECRET_ACCESS_KEY as fallbacks for MinIO credentials in app config, since these are the standard S3-compatible env var names created by operators like RustFS Manager

Closes #51

Changes

Helm (deployment.yaml, values.yaml)

• extraVolumeMounts block in spec.containers[0].volumeMounts
• extraVolumes block in spec.volumes
• env block in spec.containers[0] (after envFrom)
• Default empty-list values for env, extraVolumes, extraVolumeMounts

App code (src/config/minio.py)

• Use Pydantic AliasChoices on access_key and secret_key fields so MINIO_ACCESS_KEY is tried first, falling back to AWS_ACCESS_KEY_ID (and likewise for the secret key)

Tests (tests/unit/test_minio_config.py)

• test_loads_from_aws_env_vars_as_fallback — verifies AWS_* env vars work when MINIO_* vars are absent
• test_minio_vars_take_precedence_over_aws_vars — verifies MINIO_* vars win when both are set
• Updated get_clean_env() to also strip AWS_ACCESS_KEY_ID / AWS_SECRET_ACCESS_KEY for test isolation

Test plan

• All 1313 unit tests pass (just test-unit)
• Helm template renders correctly with default values
• Helm template renders correctly with extraVolumes, extraVolumeMounts, and env set
• Deploy with Redis TLS CA cert mounted via extraVolumes/extraVolumeMounts
• Deploy with S3 credentials from AWS_* env vars (e.g. RustFS operator secret)

🤖 Generated with Claude Code

[github-actions]

🎉 This PR is included in version 3.3.0 🎉

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