[Digital Ocean] Expand integration - App Platform components

[AleksandarCole]

Description

DigitalOcean App Platform runs apps from source (including GitHub) with managed builds and deploys. This issue tracks expanding SuperPlane’s DigitalOcean integration with components to provision, update, and tear down App Platform apps starting with create/delete and targeted updates such as environment variables (e.g. database connection strings).

Why

Adding App Platform operations lets users automate provisioning and configuration of DO-hosted apps from workflows, instead of using the control panel or API only outside SuperPlane.

Scope

Initial components:

1. digitalocean.createApp (Action)
   Provision a new App Platform app from a GitHub repository and branch (aligned with typical App Platform source configuration).

2. digitalocean.deleteApp (Action)
   Tear down an App Platform app instance.

3. digitalocean.updateApp (Action)
   Update an existing App Platform app; must include the ability to inject or update environment variables (e.g. database connection strings), in addition to any other update fields the API supports for a first slice.