fix(login): properly encode redirect URL

[utafrali]

Description

The callback URL in the login flow wasn't getting properly URL-encoded when passed as a query parameter. The auth server was rejecting the redirect because of the unescaped special characters. Switched to using url.Values to handle the encoding instead of raw string concatenation.

Related issues

Fixes #5477

Release note

Fixed login flow redirect URL encoding issue that was causing "Invalid App to redirect" errors.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 51.16%. Comparing base (8e9fb91) to head (4dd00dc).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
internal/namespaces/login/login.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5478      +/-   ##
==========================================
- Coverage   51.16%   51.16%   -0.01%     
==========================================
  Files         324      324              
  Lines       75683    75685       +2     
==========================================
  Hits        38726    38726              
- Misses      35480    35482       +2     
  Partials     1477     1477              

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[remyleone]

@utafrali thanks a lot :) could you sign your commits?

[utafrali]

Done, pushed the fix.

[remyleone]

@utafrali Could you ensure that github knows your key for the signature here: https://github.com/settings/keys Otherwise, we won't be able to merge your contribution.

[utafrali]

Got it, adding the key to my GitHub settings now.