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/pages/HomePage.vue

@@ -0,0 +1,60 @@
+<script setup lang="ts">
+import { onMounted, ref } from 'vue'
+import { useProjectCanvasStore } from '../stores/projectCanvas'
+import Canvas from '../components/Canvas.vue'
+import ProjectCanvasPage from './ProjectCanvasPage.vue'
+
+const projectCanvasStore = useProjectCanvasStore()
+const loading = ref(true)
+const showDefaultCanvas = ref(false)
+const defaultCanvasId = ref<string | null>(null)
+
+onMounted(async () => {
+  const defaultCanvas = await projectCanvasStore.fetchDefaultCanvas()
+
+  if (defaultCanvas) {
+    showDefaultCanvas.value = true
+    defaultCanvasId.value = defaultCanvas.id
+  } else {
+    showDefaultCanvas.value = false
+  }
+
+  loading.value = false
+})
+</script>
+
+<template>
+  <div v-if="loading" class="home-loading">
+    <div class="spinner"></div>
+  </div>
+
+  <ProjectCanvasPage
+    v-else-if="showDefaultCanvas && defaultCanvasId"
+    :id="defaultCanvasId"
+  />
+
+  <Canvas v-else />
+</template>
+
+<style scoped>
+.home-loading {
+  flex: 1;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  background: var(--bg-primary);
+}
+
+.spinner {
+  width: 40px;
+  height: 40px;
+  border: 3px solid var(--border-color);
+  border-top-color: var(--accent);
+  border-radius: 50%;
+  animation: spin 1s linear infinite;
+}
+
+@keyframes spin {
+  to { transform: rotate(360deg); }
+}
+</style>