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. Only tables and views the user can manage are offered, since the server adds them to the application as resources. Picking a view or table fills in an empty label.
• Ordering and nesting: entries can be dragged by their handle, and every entry has move up/down buttons plus an indent button (top-level entries) or an outdent button (child entries), so the menu can be arranged with the keyboard. A parent moves together with its children; an entry with children cannot be indented; removing a parent moves its children to the top level instead of deleting them.
• Validation: the editor checks every entry with the same rules as the server (label, target, http/https link). Errors show once a row is left, and all of them on submit; an invalid menu blocks creating the application.
• ApplicationIcon: shows a material icon by name, used for the menu item icons.
• menuItems.js: the list operations of the editor, and turning its list into the API payload, including parentIndex for nested items.
• CreateContext: sends the menu with the new application.
• Deleting an application (existing behaviour on main, not caused by this stack): the delete removes the application first, inside a transaction that is retried, so it holds the write lock before it reads. On SQLite a delete that read first failed at once when another request wrote meanwhile.
• Tests: a Cypress component test covers the list operations, and a unit test covers the delete order.

🖼️ 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