feat(contexts): edit the menu when creating an application

[remko48]

The create application dialog gets a menu editor, so an application can be created with its menu in one go.

What changes

• MenuItemsEditor: an ordered list of menu items. Each item has an icon, a label and what it opens: a view, a page with widgets, a table or an external link. Picking a target fills in an empty label.
• Ordering and nesting: entries can be dragged, and every entry also has move up/down and indent/outdent buttons, so the menu can be arranged with the keyboard. A parent moves together with its children; removing a parent moves its children to the top level instead of deleting them.
• ApplicationIcon: shows a material icon by name, used for the menu item icons.
• menuItems.js: turns the editor's list into the API payload, including parentIndex for nested items.
• CreateContext: sends the menu with the new application.

🖼️ Screenshots

🏚️ Before	🏡 After

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🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not needed
• 🔙 Backport requests are created or not needed: /backport to stableX.X
• 📅 Milestone is set
• 🌸 PR title is meaningful (if it should be in the changelog: is it meaningful to users?)

🤖 AI (if applicable)

• The content of this PR was partly or fully generated using AI