Add AppKit template to bundle init

[lennartkats-db]

Changes

• Add app-appkit to databricks bundle init, reusing the initializer behind databricks apps init.
• Support non-interactive initialization with --config-file and project_name, and update help and changelog.

Why

AppKit apps use bundles for deployment. Exposing the template through bundle init lets users find and scaffold them alongside the other bundle templates.

Tests

• ./task checks and GOTOOLCHAIN=go1.26.9 ./task lint-go passed.
• Focused Go and acceptance tests passed, including non-interactive initialization, validation, fake-server deploy, and destroy.
• An AppKit 0.76.1 scaffold initialized with closed stdin passed strict validation. On dogfood, the app reached ACTIVE and its deployment reached SUCCEEDED; the temporary app was deleted.
• Full local ./task fmt could not fetch Ruff (PyPI DNS). ./task test had failures in JSON error expectations and local Node/shell setup; the focused AppKit cases passed.
• This in-repository PR replaces [WIP] Add AppKit template to bundle init #7004, whose fork-based Actions run stopped during JFrog setup before tests could start.

Authored with Codex.

[eng-dev-ecosystem-bot]

Integration test report

Commit: f7ce88b

Run: 37939333842

	Env	✅​pass	🙈​skip	Time
✅​	aws linux-2core-8gb	276	18	4:28
✅​	aws-windows-latest-4core-16gb	278	16	3:36
✅​	azure linux-2core-8gb	275	18	4:23
✅​	azure-windows-latest-4core-16gb	277	16	4:14
✅​	gcp linux-2core-8gb	276	18	4:29
✅​	gcp-windows-latest-4core-16gb	278	16	3:41

Top 3 slowest tests (at least 2 minutes):

duration	env	testname
4:12	azure-windows-latest-4core-16gb	TestAccept
3:40	gcp-windows-latest-4core-16gb	TestAccept
3:34	aws-windows-latest-4core-16gb	TestAccept