Make dependency on Redis optional

[beeman]

Currently, the API won't start if it cannot connect to a Redis instance. However, if you only want to run this for verifying Vote identities (Validator verification) this is not needed.

Redis (and in fact, the whole queue system) should be optional and only required if the feature flags FEATURE_RESOLVER_SOLANA_FUNGIBLE or FEATURE_RESOLVER_SOLANA_NON_FUNGIBLE are enabled.

Goals:

• Be able to run the system without Redis if the above features are disabled
• If they are enabled, ensure there is a runtime check that verifies if Redis is configured and able to connect.