chore(deps): upgrade go-github to v89 and update client initialization

[chimanjain]

Description

• Upgrades the go-github from v17 (incompatible) to v89.
• Updated GitHub client initialization to use github.WithHTTPClient() option pattern (v89+ API change) with proper error handling.

Related Issue

Motivation and Context

Screenshots (if appropriate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation Update (if none of the other choices apply)

Checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 28.12%. Comparing base (cba0bbb) to head (c0ea38d).

Files with missing lines	Patch %	Lines
manager/auth/oauth/github.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4878      +/-   ##
==========================================
- Coverage   28.12%   28.12%   -0.01%     
==========================================
  Files         232      232              
  Lines       23158    23160       +2     
==========================================
  Hits         6513     6513              
- Misses      16197    16199       +2     
  Partials      448      448              

Flag	Coverage Δ
unittests	28.12% <0.00%> (-0.01%)	⬇️

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Files with missing lines	Coverage Δ
manager/auth/oauth/github.go	0.00% <0.00%> (ø)

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[gaius-qi]

LGTM