Always run API with /healthz endpoint

[mkysel]

We already have the v1/health GRPC endpoint and HTTP healthz. Our sync/indexer service without API was depending on metrics which is less robust than the existing code.

[graphite-app]

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[macroscopeapp]

Always run API server with /healthz endpoint regardless of Payer or Replication service configuration

The server now unconditionally starts the API server instead of only starting it when Payer or Replication services are enabled. The conditional check in server.go has been removed to ensure the API server and its /healthz endpoint are always available. Test utilities have been refactored to use structured configuration objects (TestServerCfg and EnabledServices structs) in server.go, and new health endpoint tests have been added in server_test.go to verify both gRPC and HTTP health checks return SERVING status when no services are explicitly enabled.

📍Where to Start

Start with the server startup logic in server.go where the conditional check for starting the API server has been removed.

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Macroscope summarized c8f2973.