Fix OAuth redirect pending actions

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Summary

This finishes the remaining OAuth popup migrations from #137, but keeps the pending action alive across the redirect round trip.

The important bit is that these flows cannot just redirect to GitHub and hope the old LiveView socket is still around. Before leaving the page, the pending action is now cached through AlgoraWeb.LocalStore; when GitHub redirects back, the page restores that state and replays the original action.

Updated flows:

• Crowdfund bounty/tip creation
• Swift bounty/tip creation
• Org bounty creation
• Org settings GitHub app installation

Fixes #137

Checks

• Parsed the touched LiveView files with Elixir's parser
• git diff --check

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