[eas-cli] set the Convex env var on EAS automatically

[FiberJW]

Why

In our Convex docs (https://docs.expo.dev/guides/using-convex/#save-the-convex-url-as-an-eas-environment-variable), we tell people to set an ENV var with EAS to use in their deployments. With our Convex integration, we can automate this step and make the setup UX even smoother.

Fixes ENG-21068

How

I added a step to the convex:connect command to set the EXPO_PUBLIC_CONVEX_URL EAS env var. If it already exists, we prompt the user to prevent accidental rewrites.

Test Plan

yarn build and using the local easd alias, run EXPO_STAGING=true easd integrations:convex:connect

You should see the new output talking about the env var, and the env var should also be visible in the env var dashboard page:

[linear]

ENG-21068

[github-actions]

Subscribed to pull request

File Patterns	Mentions
**/*	@douglowder

Generated by CodeMention

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.59%. Comparing base (4eb0753) to head (e050177).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3685      +/-   ##
==========================================
+ Coverage   56.56%   56.59%   +0.03%     
==========================================
  Files         888      888              
  Lines       38468    38490      +22     
  Branches     8022     8025       +3     
==========================================
+ Hits        21756    21778      +22     
  Misses      16614    16614              
  Partials       98       98              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[github-actions]

✅ Thank you for adding the changelog entry!