feat: implement GetCommitStatuses on forgejo

[chmouel]

📝 Description of the Change

Previously the Gitea/Forgejo provider returned nil for GetCommitStatuses, which meant the annotation matcher couldn't detect pruned-but-successful pipeline runs, causing /retest to re-run every pipeline instead of just the failed ones.

This commit replaces the stub with a real implementation that calls ListStatuses from the Forgejo SDK, maps Context→Name and State→Status, and deduplicates using a seen map. Unit tests cover happy path, deduplication, empty response, nil client, and API errors. An e2e test (TestGiteaRetestAfterPipelineRunPruning) verifies the full flow: run two pipelines, prune the PipelineRun objects, issue /retest, and assert only the failed pipeline is re-run.

🔗 Linked GitHub Issue

Jira: https://redhat.atlassian.net/browse/SRVKP-11529

🧪 Testing Strategy

• Unit tests
• Integration tests
• End-to-end tests
• Manual testing
• Not Applicable

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✅ Submitter Checklist

• 📝 My commit messages are clear, informative, and follow the project's How to write a git commit message guide. The Gitlint linter ensures in CI it's properly validated
• ✨ I have ensured my commit message prefix (e.g., fix:, feat:) matches the "Type of Change" I selected above.
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• 📖 I have added or updated documentation for any user-facing changes.
• 🧪 I have added sufficient unit tests for my code changes.
• 🎁 I have added end-to-end tests where feasible. See README for more details.
• 🔎 I have addressed any CI test flakiness or provided a clear reason to bypass it.
• If adding a provider feature, I have filled in the following and updated the provider documentation:
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[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.86%. Comparing base (69c1197) to head (a9df871).
⚠️ Report is 2 commits behind head on main.
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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2659      +/-   ##
==========================================
+ Coverage   58.80%   58.86%   +0.05%     
==========================================
  Files         206      206              
  Lines       20304    20327      +23     
==========================================
+ Hits        11940    11965      +25     
+ Misses       7591     7589       -2     
  Partials      773      773              

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[gemini-code-assist]

Code Review

This pull request implements the GetCommitStatuses method for the Gitea provider, enabling the retrieval and deduplication of commit statuses. It includes unit tests for various scenarios and a new E2E test to ensure that the /retest command correctly triggers only failed pipelines after PipelineRun pruning. The review feedback highlights a missing pagination logic in the ListStatuses calls within both the provider implementation and the E2E test, which is necessary to handle commits with a large number of statuses correctly.