[superlog] Show actionable 'wrong account' UI on invitation recipient mismatch

[superlog-app]

Summary

Users who click an org invitation link while signed in as a different account see a raw "You are not the recipient of the invitation" error with no recovery path. The invitation accept page was designed to show a friendly "This invite was sent to X, but you're signed in as Y" warning and prevent the Accept button, but that branch was dead code — better-auth's getInvitation endpoint throws 403 before returning any invitation data when the signed-in email doesn't match the invitation email.

The wrongAccount check (and the blocked Accept button) in AcceptInvitationInner could never be reached: invite.email is only populated on the success path, which is unreachable when emails don't match.

This patch adds a wrong-account state to LoadState and detects the specific 403 error message from better-auth. When triggered, the component shows a clear warning and a Sign out button so the user can sign in with the invited address and complete the flow. The dead wrongAccount variable and its associated disabled-button logic are removed.

An alternative approach would be to accept the invitation link URL without requiring authentication (serving a public preview of the invite), but that would require a better-auth API change or a custom server-side endpoint.

Incident on Superlog

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Summary by cubic

Fix wrong-account flow on org invitations by detecting recipient mismatches and showing a clear warning with a Sign out action instead of a raw error.

• Bug Fixes
  • Handle 403 from better-auth getInvitation ("You are not the recipient of the invitation") via a new wrong-account load state.
  • Show a friendly message with a Sign out button and back link so users can switch accounts and accept.
  • Remove dead wrongAccount logic and userEmail prop; Accept is only disabled during in-flight actions.

^{Written for commit 1e9efb3. Summary will update on new commits.}