feat(10-05): implement CodebergSource for Gitea REST API
- Add CodebergSource targeting /api/v1/repos/search (Codeberg + any Gitea)
- Public API by default; Authorization: token <t> when Token set
- Unauth rate limit 60/hour, authenticated ~1000/hour
- Emit Findings keyed to repo html_url with SourceType=recon:codeberg
- Keyword index maps BuildQueries output back to ProviderName
- httptest coverage: name/interface, rate limits (both modes),
sweep decoding, header presence/absence, ctx cancellation
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