fix(consul): Fix health checks for gRPC services in Docker

- Add gRPC health check support to Consul registry
  - Services are gRPC-only, not HTTP
  - Consul was trying HTTP health checks which failed
  - Now uses gRPC health checks via grpc.health.v1.Health service

- Update HealthCheckConfig to support both HTTP and gRPC
  - Add GRPC field for gRPC service name
  - Add UseGRPC flag to choose health check type
  - Default to gRPC for services (use_grpc: true in config)

- Fix service address registration in Docker
  - Services now register with Docker service name (e.g., auth-service)
  - Allows Consul to reach services via Docker network DNS
  - Falls back to localhost for local development

- Update default.yaml to enable gRPC health checks
  - Set use_grpc: true
  - Set grpc: grpc.health.v1.Health

This fixes services being deregistered from Consul due to failed
HTTP health checks. Services will now pass gRPC health checks.

internal/registry/consul/consul.go

@@ -29,7 +29,9 @@ type HealthCheckConfig struct {
 	Interval        time.Duration // Health check interval
 	Timeout         time.Duration // Health check timeout
 	DeregisterAfter time.Duration // Time to wait before deregistering unhealthy service
-	HTTP            string        // HTTP health check endpoint (e.g., "/healthz")
+	HTTP            string        // HTTP health check endpoint (e.g., "/healthz") - for HTTP services
+	GRPC            string        // gRPC health check service name (e.g., "grpc.health.v1.Health") - for gRPC services
+	UseGRPC         bool          // Whether to use gRPC health checks instead of HTTP
 }
 
 // NewRegistry creates a new Consul-based service registry.
@@ -68,7 +70,21 @@ func (r *ConsulRegistry) Register(ctx context.Context, service *registry.Service
 	}
 
 	// Add health check if configured
-	if r.config.HealthCheck.HTTP != "" {
+	if r.config.HealthCheck.UseGRPC {
+		// Use gRPC health check for gRPC services
+		// Format: host:port/service or host:port (uses default health service)
+		grpcAddr := fmt.Sprintf("%s:%d", service.Address, service.Port)
+		if r.config.HealthCheck.GRPC != "" {
+			grpcAddr = fmt.Sprintf("%s:%d/%s", service.Address, service.Port, r.config.HealthCheck.GRPC)
+		}
+		registration.Check = &consulapi.AgentServiceCheck{
+			GRPC:                           grpcAddr,
+			Interval:                       r.config.HealthCheck.Interval.String(),
+			Timeout:                        r.config.HealthCheck.Timeout.String(),
+			DeregisterCriticalServiceAfter: r.config.HealthCheck.DeregisterAfter.String(),
+		}
+	} else if r.config.HealthCheck.HTTP != "" {
+		// Use HTTP health check for HTTP services
 		healthCheckURL := fmt.Sprintf("http://%s:%d%s", service.Address, service.Port, r.config.HealthCheck.HTTP)
 		registration.Check = &consulapi.AgentServiceCheck{
 			HTTP:                           healthCheckURL,