Complete tasks 4.1-4.2: Page management service and HTTP endpoints

- Implemented PageService with full CRUD operations
- Added GetPages, CreatePage, UpdatePage, DeletePage, ReorderPages methods
- Cascade deletion of widgets when page is deleted
- Prevention of last page deletion
- Created page HTTP endpoints (GET, POST, PUT, DELETE, reorder)
- HTMX-friendly HTML fragment responses
- Comprehensive unit tests for service and handlers
- Updated dashboard to use PageService and create default pages

internal/services/interfaces.go

@@ -0,0 +1,17 @@
+package services
+
+import (
+	"context"
+
+	"custom-start-page/internal/models"
+)
+
+// PageServiceInterface defines the interface for page operations
+type PageServiceInterface interface {
+	GetPages(ctx context.Context, userID string) ([]*models.Page, error)
+	CreatePage(ctx context.Context, userID, name string) (*models.Page, error)
+	CreateDefaultPage(ctx context.Context, userID string) (*models.Page, error)
+	UpdatePage(ctx context.Context, userID, pageID, name string) (*models.Page, error)
+	DeletePage(ctx context.Context, userID, pageID string) error
+	ReorderPages(ctx context.Context, userID string, pageOrder []string) error
+}