Add Redis Sentinel support for Sidekiq high availability (#457)

* Initial plan

* Add Redis Sentinel support for Sidekiq configuration

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

* Add documentation for Redis Sentinel configuration

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

* Improve Sentinel host parsing with better validation and error handling

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

* Add port validation to prevent invalid Sentinel configurations

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

* Linter

* Add Sentinel authentication credentials to fix NOAUTH error

- Add sentinel_username (defaults to "default")
- Add sentinel_password (uses REDIS_PASSWORD)
- Update documentation for sentinel auth configuration

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

* Add CHANGELOG.md for Helm chart documenting Redis Sentinel support

Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>

* Set REDIS_URL alongside in Sentinel mode also

---------

Signed-off-by: Juan José Mata <juanjo.mata@gmail.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: jjmata <187772+jjmata@users.noreply.github.com>
Co-authored-by: Juan José Mata <juanjo.mata@gmail.com>

.env.example

@@ -70,8 +70,16 @@ POSTGRES_PASSWORD=postgres
 POSTGRES_USER=postgres
 
 # Redis configuration
+# Standard Redis URL (for direct connection)
 REDIS_URL=redis://localhost:6379/1
 
+# Redis Sentinel configuration (for high availability)
+# When REDIS_SENTINEL_HOSTS is set, it takes precedence over REDIS_URL
+# REDIS_SENTINEL_HOSTS=sentinel1:26379,sentinel2:26379,sentinel3:26379
+# REDIS_SENTINEL_MASTER=mymaster
+# REDIS_SENTINEL_USERNAME=default
+# REDIS_PASSWORD=your-redis-password
+
 # App Domain
 # This is the domain that your Sure instance will be hosted at. It is used to generate links in emails and other places.
 APP_DOMAIN=