refactor(core): remove scheduler and simplify app lifecycle

- Delete scheduler.go and scheduler_test.go (no longer needed)
- Simplify App struct by removing Handler interface dependency
- Remove StartScheduler/StopScheduler from app lifecycle
- Update main.go to not pass handler to app constructor
- Remove scheduler mock from app tests, simplify test coverage

internal/app/app.go

@@ -12,26 +12,18 @@ import (
 	"github.com/labstack/echo/v4"
 )
 
-// Handler interface for services that need lifecycle management
-type Handler interface {
-	StartScheduler()
-	StopScheduler()
-}
-
 // App manages application lifecycle and graceful shutdown
 type App struct {
 	echo            *echo.Echo
-	handler         Handler
 	shutdownTimeout time.Duration
 	shutdownMutex   sync.Mutex
 	shutdownDone    chan struct{}
 }
 
 // New creates a new App instance
-func New(echo *echo.Echo, handler Handler) *App {
+func New(echo *echo.Echo) *App {
 	return &App{
 		echo:            echo,
-		handler:         handler,
 		shutdownTimeout: 30 * time.Second,
 		shutdownDone:    make(chan struct{}),
 	}
@@ -41,9 +33,6 @@ func New(echo *echo.Echo, handler Handler) *App {
 func (a *App) Start() error {
 	log.Println("Starting application lifecycle management...")
 
-	// Start background services
-	a.startBackgroundServices()
-
 	// Setup signal handling for graceful shutdown
 	sigChan := make(chan os.Signal, 1)
 	signal.Notify(sigChan,
@@ -66,20 +55,6 @@ func (a *App) Start() error {
 	return nil
 }
 
-// startBackgroundServices starts all background services
-func (a *App) startBackgroundServices() {
-	log.Println("Starting background services...")
-
-	// Start scheduler for auto-scanning
-	go func() {
-		a.handler.StartScheduler()
-		log.Println("Scheduler started")
-	}()
-
-	// Note: Watch mode is started by the handlers package
-	// after a 2-second delay, so we don't duplicate it here
-}
-
 // Shutdown performs graceful shutdown of all services
 func (a *App) Shutdown() error {
 	a.shutdownMutex.Lock()
@@ -112,10 +87,6 @@ func (a *App) Shutdown() error {
 			log.Printf("Error stopping HTTP server: %v", err)
 		}
 
-		// Stop scheduler
-		log.Println("Stopping scheduler...")
-		a.handler.StopScheduler()
-
 		log.Println("All services stopped")
 	}()