Fix profile contribution links for grouped repos

[GHX5T-SOL]

Fixes #168.

Summary

• Link profile contribution cards to an owner-scoped GitHub merged-PR search instead of the first repository in the owner group.
• Add a LiveView regression covering two repositories under the same organization owner.

Validation

• TEST_DATABASE_URL=postgresql://postgres:postgres@localhost:15432/algora_test mix test test/algora_web/live/user/profile_live_test.exs (1 test, 0 failures; local run still prints existing Oban sandbox shutdown logs after ExUnit completes)
• mix format --check-formatted lib/algora_web/live/user/profile_live.ex test/algora_web/live/user/profile_live_test.exs
• git diff --check
• git diff HEAD~1..HEAD | gitleaks detect --pipe --no-banner --redact

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