* Auto-create mobile OAuth application when missing (#912)
Self-hosted users who set up their instance without running `db:seed`
(or reset their database) got "Record not found" on mobile login because
`MobileDevice.shared_oauth_application` used `find_by!` which raises
when the "Sure Mobile" Doorkeeper application does not exist.
Switch to `find_or_create_by!` so the record is created transparently
on first use, matching the attributes from the seed file.
* Nice Claude Code suggestion
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Co-authored-by: Juan José Mata <jjmata@jjmata.com>
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