feat: Add reject reason

[andypols]

Summary

This PR addresses #1030. Previously, push rejections were recorded without any context. Reviewers now must provide an explanation when rejecting a push, and that explanation is stored and displayed so contributors can understand why their changes were not approved.

Solution

Backend

• Database
  • Updated db.reject (file and Mongo) to accept a rejection object.
  • Persist the rejection on the Action via a new rejection property.
• Push API
  • Updated POST /push/:id/reject to require a rejection reason.
  • Fetches the reviewer email (similar to approvals) and blocks the rejection if it’s missing.
  • Saves the rejection payload including:
    • reason
    • timestamp
    • reviewer

UI

• Refactored PushDetails into smaller components for clarity and easier maintenance:
  • PushStatusHeader
  • StatusIcon
  • Attestation
  • Rejection
  • ApprovalBadge
  • RejectionBadge
• Added a Rejection dialog that requires the reviewer to enter a reason before rejecting a push.
• Added RejectionBadge and ApprovalBadge components to display:
  • reviewer
  • timestamp
  • rejection details (for rejections)

[netlify]

✅ Deploy Preview for endearing-brigadeiros-63f9d0 canceled.

Name	Link
🔨 Latest commit	28e25b0
🔍 Latest deploy log	https://app.netlify.com/projects/endearing-brigadeiros-63f9d0/deploys/692b4b4cf7405300085a5e1f

[codecov]

Codecov Report

❌ Patch coverage is 96.66667% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 80.45%. Comparing base (9f24d3f) to head (28e25b0).

Files with missing lines	Patch %	Lines
src/db/mongo/pushes.ts	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1295      +/-   ##
==========================================
- Coverage   83.35%   80.45%   -2.91%     
==========================================
  Files          70       72       +2     
  Lines        3004     3162     +158     
  Branches      499      539      +40     
==========================================
+ Hits         2504     2544      +40     
- Misses        397      516     +119     
+ Partials      103      102       -1     

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