Implements issue 19:

• Convert the admin editor into a workspace shell with sticky header, main canvas, and metadata rail
• Make admin navigation collapsible on desktop and dialog-based on mobile
• Expand TipTap controls and add custom highlight/text-align support
• Gate HTML source mode to rich text fields that explicitly allow it
• Route rich editor image uploads through the shared image pipeline

Validation:

• CI=true corepack yarn test --runInBand client-src/components/AdminNavApp/AdminNavApp.test.jsx client-src/ClientAdminItemsApp/components/SchemaItemEditor/SchemaItemEditor.test.jsx client-src/components/FormRenderer/FormRenderer.test.jsx client-src/components/AdminRichEditor/AdminRichEditor.test.jsx client-src/components/AdminRichEditor/component/RichEditorTiptap/RichEditorTiptap.test.jsx client-src/components/AdminRichEditor/component/RichEditorMediaDialog/RichEditorMediaDialog.test.jsx client-src/components/FormRenderer/widgets/MediaWidgets.test.jsx

DB note:

• No schema changes were needed for this issue. The deploy workflow already runs setup:production, and ops/init_feed_db.js applies migrations before init.sql during deploy.