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

server/db/migrations.ts

@@ -119,7 +119,8 @@ function runColumnMigrations(db: Database) {
   const alterStatements = [
     'ALTER TABLE project_canvas ADD COLUMN show_in_toolbar INTEGER DEFAULT 0',
     'ALTER TABLE project_canvas ADD COLUMN toolbar_icon TEXT',
-    'ALTER TABLE project_canvas ADD COLUMN toolbar_order INTEGER DEFAULT 99'
+    'ALTER TABLE project_canvas ADD COLUMN toolbar_order INTEGER DEFAULT 99',
+    'ALTER TABLE project_canvas ADD COLUMN status TEXT DEFAULT \'active\''
   ]
 
   for (const sql of alterStatements) {