Fix error message format to comply with linter requirements

[Copilot]

The linter enforces that error messages must start with "failed to" followed by the action that failed. Line 639 in pkg/api/authn.go used the pattern "bearer authentication failed" which violates this rule.

Changes

• Updated error message in bearer authentication handler from "bearer authentication failed" to "failed to authenticate with bearer token"

This aligns with the existing error message pattern used throughout the codebase:

// Before
ctlr.Log.Error().Msg("bearer authentication failed")

// After  
ctlr.Log.Error().Msg("failed to authenticate with bearer token")

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[codecov]

Codecov Report

❌ Patch coverage is 67.32026% with 50 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.43%. Comparing base (708adf6) to head (3218241).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/api/authn.go	48.21%	27 Missing and 2 partials ⚠️
pkg/api/bearer_oidc.go	76.66%	17 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3705      +/-   ##
==========================================
- Coverage   91.58%   91.43%   -0.16%     
==========================================
  Files         186      187       +1     
  Lines       26499    26619     +120     
==========================================
+ Hits        24270    24339      +69     
- Misses       1444     1487      +43     
- Partials      785      793       +8     

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