release: cut 0.2.1

Publish releases to the Codeberg mirror (signed APK + SHA-256 checksum)
as a direct-download channel. Bumps versionName to 0.2.1; the pipeline
mints the v0.2.1 tag on merge to main.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/build.gradle.kts

@@ -29,8 +29,8 @@ android {
         // release itself (versionCode is pinned to MAJOR*10000 + MINOR*100 +
         // PATCH from versionName, e.g. 0.2.0 -> 200). The Gitea release is marked
         // as a pre-release while MAJOR is 0. See docs/RELEASING.md.
-        versionCode = 200
-        versionName = "0.2.0"
+        versionCode = 201
+        versionName = "0.2.1"
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }