Add maintainer role for Devvit apps

[CR29-22-2805]

Related to #272

💸 TL;DR

This prototypes CLI-side support for a maintainer role on Devvit apps. Owners and designated maintainers would be allowed to upload and publish app versions, while unrelated users would remain unauthorized.

This is intended to reduce deployment bottlenecks for mature, collaboratively maintained apps without granting full app ownership.

📜 Details

Design Doc: N/A

Jira: N/A

This patch adds a shared CLI authorization helper for app write actions and updates the upload/publish commands to use it.

The new helper recognizes three authorization outcomes:

• owner
• maintainer
• unauthorized

Owners and maintainers can write app versions. Unauthorized users cannot.

This patch updates:

• upload.ts to allow app uploads by owners or maintainers.
• publish.ts to allow app publishing by owners or maintainers.
• The publish authorization error message so it refers to the owner or a designated maintainer.
• Unit coverage for owner, maintainer, unauthorized, and maintainer-aware error-message behavior.

This is a CLI-side prototype. It assumes app metadata can expose a maintainers list or equivalent backend-provided permission source. Backend/proto support and rollback support would need to be implemented separately.

🧪 Testing Steps / Validation

Testing:

• Added unit tests for app authorization helper behavior.
• Covered owner, designated maintainer, and unauthorized-user authorization outcomes.
• Covered the maintainer-aware publish error message.
• Confirmed in code review that the Reddit employee override path is unchanged.
• Ran git diff --check.
• Attempted yarn install from the workspace root, but dependency installation failed because packages/apps/devvit-dev-bot/package.json depends on devvit@0.13.6-dev, which was not available from the public npm registry.
• Because dependencies could not be installed, I could not run yarn test or yarn lint locally.

✅ Checks

• CI tests (if present) are passing
• Adheres to code style for repo
• Contributor License Agreement (CLA) completed if not a Reddit employee