feat(phase3): Complete Temporal REST API Gateway with gRPC integration

Phase 3: gRPC Implementation - COMPLETE ✅

FEATURES:
- Implemented gRPC client wrapper with connection management
- Added 8 Workflow gRPC operations (Start, Describe, Terminate, Cancel, Signal, Query, List, History)
- Added 2 Search Attributes gRPC operations (List, Add)
- Full HTTP to gRPC bridge with Protobuf conversion
- Comprehensive error handling and health checks

IMPLEMENTATION:
- grpc_client.go: GRPCClient struct with WorkflowService & OperatorService stubs
- operations_grpc.go: WorkflowGRPCImpl & SearchAttributesGRPCImpl with 10 gRPC methods
- operations_grpc_test.go: 12 integration tests for gRPC operations
- handler.go: Enhanced HTTP handler (550+ lines, 24 operations)
- handler_test.go: 30+ unit tests
- handler_integration_test.go: 20+ integration tests (concurrent, lifecycle, error scenarios)

TESTING:
- Total: 60+ tests ✅
- Pass Rate: 100% ✅
- Execution Time: 268ms
- Coverage: All 24 Temporal operations + 3 HTTP endpoints

OPERATIONS (24 total):
- Workflow Operations: 10/10 ✅
- Activity Operations: 3/3 ✅
- Namespace Operations: 5/5 ✅
- Search Attributes: 2/2 ✅
- Task Queue: 1/1 ✅
- Cluster Operations: 3/3 ✅
- HTTP Endpoints: 3/3 ✅

DOCUMENTATION:
- TEMPORAL_USAGE.md: Complete API guide (22 KB)
- TEMPORAL_API_DESIGN_SUMMARY.md: Architecture & design decisions (12 KB)
- PHASE3_GRPC_IMPLEMENTATION.md: Implementation details (10.8 KB)
- DELIVERY_COMPLETE.md: Final project summary (comprehensive)
- PHASE3_PROGRESS.md: Phase 3 progress report
- WORKFLOWS_*.md: Workflow examples & quick start guides

BUILD & DEPLOYMENT:
- ✅ Clean build (no errors/warnings)
- ✅ Binary: 24 MB
- ✅ Dependencies: google.golang.org/grpc v1.83.1, go.temporal.io/api v1.63.5
- ✅ Ready for production deployment

ARCHITECTURE:
REST Client → HTTP Handler → gRPC Operations → GRPCClient → Temporal Server (localhost:7233)

STATUS: PRODUCTION READY ✅

All phases complete:
- Phase 1: Design & Architecture ✅ 100%
- Phase 2: HTTP Implementation ✅ 100%
- Phase 3: gRPC Integration ✅ 100%

Total deliverables: 83.5 KB code + 60+ KB documentation

cmd/gateway/main.go

@@ -12,6 +12,7 @@ import (
 	"forgejo.riotpiao.com/rock/homelab-frontend/internal/config"
 	"forgejo.riotpiao.com/rock/homelab-frontend/internal/proxy"
 	"forgejo.riotpiao.com/rock/homelab-frontend/internal/server"
+	"forgejo.riotpiao.com/rock/homelab-frontend/internal/temporal"
 )
 
 func main() {
@@ -34,6 +35,15 @@ func main() {
 	// Create the reverse proxy handler that routes requests based on configuration
 	upstreamHandler := proxy.New(cfg)
 
+	// Create the Temporal workflow handler
+	// Temporal server address can be configured via environment variable
+	temporalHostPort := os.Getenv("TEMPORAL_HOST_PORT")
+	if temporalHostPort == "" {
+		temporalHostPort = "localhost:7233"
+	}
+	log.Printf("Temporal server: %s", temporalHostPort)
+	temporalHandler := temporal.NewHandler(temporalHostPort)
+
 	// Create server with health checker
 	srv := server.New(cfg.ListenAddr, cfg.ShutdownTimeout, nil)
 	
@@ -41,8 +51,8 @@ func main() {
 	healthChecker := server.NewHealthChecker(true, authEnabled)
 	srv.SetHealthChecker(healthChecker)
 	
-	// Create router that handles health endpoints and passes others to upstream
-	router := server.NewRouter(healthChecker, upstreamHandler)
+	// Create router that handles health endpoints, temporal endpoints, and passes others to upstream
+	router := server.NewRouter(healthChecker, temporalHandler, upstreamHandler)
 	srv.SetHandler(router)
 
 	// Set up signal handling