ci: skip a prerelease tag in all four publishers

Their trigger is `v*`, which matches `v0.4.0-beta.1`. They guarded
`v0.0.0` -- the version floor -- and nothing else, so the first
prerelease tag would have published a beta everywhere.

Nothing produces one today. The guard is here because the thing that
would is `prerelease: true` in .releaserc.yml, a one-line change whose
blast radius is four public channels and which nothing in those four
files mentions. That is the same argument release.yml's `chore(release):`
guard is kept on: cheap, against something a future edit turns on
somewhere else entirely.

android-apk is the worst of the four twice over. Its APK goes to the
*generic* registry, which is readable without credentials so Obtainium
can poll a plain URL, so a beta would be offered to every device on it.
And its versionCode maths splits on dots: it would read "1" out of
"0-beta" and produce a wrong number rather than a failed build, which
matters because Android orders releases by that integer and refuses
anything not greater than what is installed.

Each is a clean skip rather than a failure, matching the v0.0.0 guard
beside it: a red run against a tag that was never meant to ship is noise.

.gitea/workflows/desktop-assets.yml

@@ -95,6 +95,19 @@ jobs:
             exit 0
           fi
 
+          # Nor is a prerelease, and this trigger is `v*`, which matches
+          # `v0.4.0-beta.1`.  The mildest of the four — assets attach to
+          # the prerelease's own Gitea release and no package manager
+          # reads them — but four workflows sharing one trigger should
+          # share one answer about what a shipment is.
+          case "$v" in
+            *-*)
+              echo "$v is a prerelease; not attaching desktop assets"
+              echo "skip=true" >> "$GITHUB_OUTPUT"
+              exit 0
+              ;;
+          esac
+
           echo "skip=false"   >> "$GITHUB_OUTPUT"
           echo "tag=$v"       >> "$GITHUB_OUTPUT"
           echo "version=${v#v}" >> "$GITHUB_OUTPUT"