feat: Add multi-canvas system with project canvas support

- Add project_canvas and canvas_components tables for persistent canvas storage
- Add ProjectCanvas store with full CRUD operations
- Add ProjectCanvasPage for rendering saved canvas with components
- Add ProjectsPage for managing canvas list (create, clone, delete)
- Add HomePage that loads default canvas or falls back to dynamic canvas
- Add toolbar support for displaying canvas as pages with custom icons
- Add component usage validation to prevent deletion of components in use
- Add MCP tools for canvas management (list, create, update, delete, clone)
- Update router with /canvas/:id and /projects routes
- Update Toolbar to show dynamic canvas pages from database

frontend/src/types/canvas.ts

@@ -0,0 +1,71 @@
+export type CanvasType = 'dynamic' | 'project' | 'system' | 'external'
+
+export interface CanvasConfig {
+  layout?: 'free' | 'grid' | 'stack'
+  settings?: {
+    backgroundColor?: string
+    padding?: string
+    gridColumns?: number
+    gridGap?: string
+  }
+  permissions?: {
+    canAddComponents?: boolean
+    canRemoveComponents?: boolean
+    canEditTools?: boolean
+    canChangeTheme?: boolean
+  }
+}
+
+export interface ProjectCanvas {
+  id: string
+  name: string
+  description?: string
+  type: CanvasType
+  theme_id?: string | null
+  config: CanvasConfig | null
+  tools: string[]
+  is_default: boolean
+  is_system: boolean
+  show_in_toolbar: boolean
+  toolbar_icon?: string | null
+  toolbar_order: number
+  created_at?: string
+  updated_at?: string
+}
+
+export interface CanvasComponentLayout {
+  x: number
+  y: number
+  width: number
+  height: number
+}
+
+export interface CanvasComponent {
+  id: number
+  canvasId: string
+  componentId: string
+  position: number
+  props: Record<string, any>
+  layout: CanvasComponentLayout | null
+  isVisible: boolean
+  createdAt?: string
+  component?: {
+    id: string
+    name: string
+    template: string
+    setup?: string
+    style?: string
+    props?: string[]
+    imports?: string[]
+  }
+}
+
+export interface ComponentUsage {
+  componentId: string
+  usedBy: Array<{
+    id: string
+    name: string
+    type: CanvasType
+  }>
+  canDelete: boolean
+}