Update CreateConnectionCommand to carry PrimaryConnectionDetails,
BackupConnectionDetails, and FailoverRetryCount. Update all callers:
DataConnectionManagerActor, DataConnectionActor, DeploymentManagerActor,
FlatteningService, and ConnectionConfig. The actor stores both configs
but continues using primary only — failover logic comes in Task 3.
DataConnectionActor now calls UpdateConnectionHealth() on state
transitions (Connecting/Connected/Reconnecting) and UpdateTagResolution()
on connection establishment. DataConnectionManagerActor calls
RemoveConnection() on actor removal. Health reports now include
data connection statuses when instances are deployed with bindings.