feat(epic2): Implement core authentication and authorization services

- Implement Audit Service (2.5)
  - gRPC server with Record and Query operations
  - Database persistence with audit schema
  - Service registry integration
  - Entry point: cmd/audit-service

- Implement Identity Service (2.2)
  - User CRUD operations
  - Password hashing with argon2id
  - Email verification and password reset flows
  - Entry point: cmd/identity-service
  - Fix package naming conflicts in user_service.go

- Implement Auth Service (2.1)
  - JWT token generation and validation
  - Login, RefreshToken, ValidateToken, Logout RPCs
  - Integration with Identity Service
  - Entry point: cmd/auth-service
  - Note: RefreshToken entity needs Ent generation

- Implement Authz Service (2.3, 2.4)
  - Permission checking and authorization
  - User roles and permissions retrieval
  - RBAC-based authorization
  - Entry point: cmd/authz-service

- Implement gRPC clients for all services
  - Auth, Identity, Authz, and Audit clients
  - Service discovery integration
  - Full gRPC communication

- Add service configurations to config/default.yaml
- Create SUMMARY.md with implementation details and testing instructions
- Fix compilation errors in Identity Service (password package conflicts)
- All services build successfully and tests pass

Makefile

@@ -125,11 +125,23 @@ generate-proto:
 		echo "protoc-gen-go-grpc not found. Install with: go install google.golang.org/grpc/cmd/protoc-gen-go-grpc@latest"; \
 		exit 1; \
 	fi
-	@mkdir -p api/proto/generated
+	@mkdir -p api/proto/generated/audit/v1 api/proto/generated/auth/v1 api/proto/generated/authz/v1 api/proto/generated/identity/v1
 	@protoc --go_out=api/proto/generated --go_opt=paths=source_relative \
 		--go-grpc_out=api/proto/generated --go-grpc_opt=paths=source_relative \
 		--proto_path=api/proto \
-		api/proto/*.proto
+		api/proto/audit.proto
+	@protoc --go_out=api/proto/generated --go_opt=paths=source_relative \
+		--go-grpc_out=api/proto/generated --go-grpc_opt=paths=source_relative \
+		--proto_path=api/proto \
+		api/proto/auth.proto
+	@protoc --go_out=api/proto/generated --go_opt=paths=source_relative \
+		--go-grpc_out=api/proto/generated --go-grpc_opt=paths=source_relative \
+		--proto_path=api/proto \
+		api/proto/authz.proto
+	@protoc --go_out=api/proto/generated --go_opt=paths=source_relative \
+		--go-grpc_out=api/proto/generated --go-grpc_opt=paths=source_relative \
+		--proto_path=api/proto \
+		api/proto/identity.proto
 	@echo "gRPC code generation complete"
 
 verify: fmt-check lint test