add optional TLS for Redis Sentinel connections via env flag

[Devenir-Glorieux]

Describe the feature or potential improvement

Langfuse currently supports Redis TLS via REDIS_TLS_ENABLED, but in Sentinel mode it does not expose a dedicated env-controlled way to enable TLS for Sentinel endpoints themselves.

In TLS-only Sentinel setups, this forces downstream users to patch built artifacts in Docker images.
In createRedisSentinelInstance we already pass ...tlsOptions, but Sentinel-specific TLS options are not conditionally controlled via env:

• enableTLSForSentinelMode
• sentinelTLS

As a result, users cannot configure Sentinel TLS cleanly through documented environment variables.

Proposal: add a new env variable:
REDIS_SENTINEL_TLS_ENABLED (true|false, default false)

• REDIS_SENTINEL_TLS_ENABLED only has effect when REDIS_SENTINEL_ENABLED=true.
• Effective Sentinel TLS requires REDIS_TLS_ENABLED=true (so TLS options exist).
• Default behavior remains backward-compatible unless REDIS_SENTINEL_TLS_ENABLED=true is explicitly set.

https://redis.github.io/ioredis/interfaces/SentinelConnectionOptions.html#enableTLSForSentinelMode

Additional information

No response

[Devenir-Glorieux]

Linked PR: #13360

[Steffen911]

Merged! Thank you.