Add a supported App Page renderer extension contract

[thsnkhn]

Problem

App Page metadata can select only framework-bundled renderers. The Studio registry has no supported way to discover or load an App-owned operational page. Apps that need an interaction beyond global Record forms and lists must fork Studio or add private framework code.

Required behavior

• Define a versioned App Page extension contract.
• Let an installed App declare its frontend entry point and renderer names.
• Load App assets through an explicit allowlisted mechanism with clear failure states.
• Provide permission-aware clients for Records, actions, files, and activity.
• Isolate renderer registration and reject name collisions.
• Define compatibility checks between the App bundle and Studio contract version.
• Keep global CRUD and report renderers framework-owned.

Acceptance criteria

• An installed App can provide a Page renderer without modifying framework source.
• Studio discovers and loads the renderer from App metadata.
• Missing, incompatible, or failed bundles show an actionable error and do not break Studio boot.
• The renderer cannot bypass server-side permissions.
• The contract and packaging workflow are documented for generated projects.

[thsnkhn]

Developers should be able to create custom pages using vuejs. they can either use our own design system (tonic) or style their own