refactor: Align Epic 0 & Epic 1 with true microservices architecture

Refactor core kernel and infrastructure to support true microservices
architecture where services are independently deployable.

Phase 1: Core Kernel Cleanup
- Remove database provider from CoreModule (services create their own)
- Update ProvideHealthRegistry to not depend on database
- Add schema support to database client (NewClientWithSchema)
- Update main entry point to remove database dependency
- Core kernel now provides only: config, logger, error bus, health, metrics, tracer, service registry

Phase 2: Service Registry Implementation
- Create ServiceRegistry interface (pkg/registry/registry.go)
- Implement Consul registry (internal/registry/consul/consul.go)
- Add Consul dependency (github.com/hashicorp/consul/api)
- Add registry configuration to config/default.yaml
- Add ProvideServiceRegistry() to DI container

Phase 3: Service Client Interfaces
- Create service client interfaces:
  - pkg/services/auth.go - AuthServiceClient
  - pkg/services/identity.go - IdentityServiceClient
  - pkg/services/authz.go - AuthzServiceClient
  - pkg/services/audit.go - AuditServiceClient
- Create ServiceClientFactory (internal/client/factory.go)
- Create stub gRPC client implementations (internal/client/grpc/)
- Add ProvideServiceClientFactory() to DI container

Phase 4: gRPC Service Definitions
- Create proto files for all core services:
  - api/proto/auth.proto
  - api/proto/identity.proto
  - api/proto/authz.proto
  - api/proto/audit.proto
- Add generate-proto target to Makefile

Phase 5: API Gateway Implementation
- Create API Gateway service entry point (cmd/api-gateway/main.go)
- Create Gateway implementation (services/gateway/gateway.go)
- Add gateway configuration to config/default.yaml
- Gateway registers with Consul and routes requests to backend services

All code compiles successfully. Core services (Auth, Identity, Authz, Audit)
will be implemented in Epic 2 using these foundations.

cmd/platform/main.go

@@ -7,23 +7,28 @@ import (
 	"os"
 
 	"git.dcentral.systems/toolz/goplt/internal/di"
-	"git.dcentral.systems/toolz/goplt/internal/infra/database"
-	"git.dcentral.systems/toolz/goplt/internal/server"
+	"git.dcentral.systems/toolz/goplt/internal/health"
+	"git.dcentral.systems/toolz/goplt/internal/metrics"
+	"git.dcentral.systems/toolz/goplt/pkg/config"
 	"git.dcentral.systems/toolz/goplt/pkg/logger"
 	"go.uber.org/fx"
 )
 
 func main() {
 	// Create DI container with lifecycle hooks
-	// We need to invoke the HTTP server to ensure all providers execute
+	// This is a minimal entry point for testing core kernel infrastructure
+	// Services will have their own entry points (cmd/{service}/main.go)
 	container := di.NewContainer(
 		// Invoke lifecycle hooks
 		fx.Invoke(di.RegisterLifecycleHooks),
-		// Force HTTP server to be created (which triggers all dependencies)
-		// This ensures database, health, metrics, etc. are all created
-		fx.Invoke(func(_ *server.Server, _ *database.Client) {
-			// Both server and database are created, hooks are registered
-			// This ensures all providers execute
+		// Verify core kernel services are available
+		fx.Invoke(func(
+			_ config.ConfigProvider,
+			_ logger.Logger,
+			_ *health.Registry,
+			_ *metrics.Metrics,
+		) {
+			// Core kernel services are available
 		}),
 	)