feat: Add canvas gallery with soft delete, snapshots and components

Replace the empty dynamic canvas placeholder with a gallery showing
saved canvases, snapshots and Vue components. Users can create new
canvases, restore snapshots, load components, and manage canvas
toolbar/archive settings from the gallery.

- Backend: soft delete (archive) instead of hard delete, status column
- Frontend: CanvasGallery component with grid, search, settings popover
- Show canvas name in global header when viewing a project canvas
- Remove ProjectsPage (replaced by gallery), clean all references
- MCP tools: project category available on canvas page, update handlers

frontend/src/stores/projectCanvas.ts

@@ -31,6 +31,14 @@ export const useProjectCanvasStore = defineStore('projectCanvas', () => {
     canvases.value.find(c => c.type === 'dynamic')
   )
 
+  const activeCanvasesList = computed(() =>
+    canvases.value.filter(c => c.status !== 'archived')
+  )
+
+  const archivedCanvases = computed(() =>
+    canvases.value.filter(c => c.status === 'archived')
+  )
+
   const canvasCount = computed(() => canvases.value.length)
 
   const hasActiveCanvas = computed(() => activeCanvas.value !== null)
@@ -38,11 +46,12 @@ export const useProjectCanvasStore = defineStore('projectCanvas', () => {
   const hasDefaultCanvas = computed(() => defaultCanvas.value !== null)
 
   // Actions
-  async function fetchCanvases() {
+  async function fetchCanvases(includeArchived = false) {
     loading.value = true
     error.value = null
     try {
-      const res = await fetch(`${API_URL}/api/canvas`)
+      const url = includeArchived ? `${API_URL}/api/canvas?include_archived=true` : `${API_URL}/api/canvas`
+      const res = await fetch(url)
       if (!res.ok) throw new Error('Failed to fetch canvases')
       canvases.value = await res.json()
     } catch (e) {
@@ -168,6 +177,10 @@ export const useProjectCanvasStore = defineStore('projectCanvas', () => {
     }
   }
 
+  async function restoreCanvas(id: string): Promise<boolean> {
+    return updateCanvas(id, { status: 'active' } as any)
+  }
+
   async function cloneCanvas(id: string, newName?: string): Promise<string | null> {
     saving.value = true
     error.value = null
@@ -304,6 +317,8 @@ export const useProjectCanvasStore = defineStore('projectCanvas', () => {
     projectCanvases,
     systemCanvases,
     dynamicCanvas,
+    activeCanvasesList,
+    archivedCanvases,
     canvasCount,
     hasActiveCanvas,
     hasDefaultCanvas,
@@ -315,6 +330,7 @@ export const useProjectCanvasStore = defineStore('projectCanvas', () => {
     createCanvas,
     updateCanvas,
     deleteCanvas,
+    restoreCanvas,
     cloneCanvas,
     fetchCanvasComponents,
     addComponentToCanvas,