Most forges hand back a "latest stable" that ignores prereleases. Fine
until something ships only prereleases for a stretch — us, through
alpha, where every tag under v0.3.0 goes out as a prerelease. Against
that, /releases/latest either freezes or returns nothing, and the
dashboard reads like nothing's moving.
Add a per-row track_prereleases flag. When it's on, the forgejo adapter
walks the full release list and considers prereleases when picking the
highest version; off (the default) keeps stable-only behavior, so the
other adapters don't change. Seed our own self-row on so we stop
looking frozen.
Renamed gitea_releases to forgejo_releases while in there — the wire
format is Forgejo's, Codeberg runs it, and the old name was a misnomer.
Legacy source="gitea" rows still resolve through an alias.
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