Enhance notification APIs with HTML email support, CC/BCC, and structured logging

Add comprehensive improvements across REST and gRPC APIs:
  - Add structured logging for all notification operations
  - Implement HTML email support with multipart/alternative MIME
  - Add CC and BCC recipient support for email notifications
  - Add GetNotifiers endpoint to query available notifier configurations
  - Support configurable From name in SMTP configuration
  - Auto-detect content type (text vs HTML) in notification bodies
  - Improve error handling and validation across all endpoints

  🤖 Generated with [Claude Code](https://claude.com/claude-code)

  Co-Authored-By: Claude <noreply@anthropic.com>

api/rest/router.go

@@ -5,11 +5,12 @@ import (
 
 	"github.com/gorilla/mux"
 	"github.com/igodwin/notifier/internal/domain"
+	"github.com/igodwin/notifier/internal/logging"
 )
 
 // NewRouter creates a new HTTP router with all routes configured
-func NewRouter(service domain.NotificationService) *mux.Router {
-	handler := NewHandler(service)
+func NewRouter(service domain.NotificationService, logger *logging.Logger) *mux.Router {
+	handler := NewHandler(service, logger)
 	router := mux.NewRouter()
 
 	// API v1 routes
@@ -26,6 +27,9 @@ func NewRouter(service domain.NotificationService) *mux.Router {
 	// Stats route
 	v1.HandleFunc("/stats", handler.GetStats).Methods(http.MethodGet)
 
+	// Notifiers route
+	v1.HandleFunc("/notifiers", handler.GetNotifiers).Methods(http.MethodGet)
+
 	// Health check route
 	router.HandleFunc("/health", handler.HealthCheck).Methods(http.MethodGet)