build: the F-Droid repository shows the app's icon

fdroid finds a launcher icon only under res/<folder>/<name>.png, and
release APKs shorten the resources' paths (res/9w.png; fdroidserver
issue 885), so the app showed no icon in the F-Droid app.
tool/fdroid_repo.sh now gives it the snap's icon in the metadata
(metadata/app.halkyon.learn/en-US/icon.png), as the repository's own.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

tool/fdroid_repo.sh

@@ -83,6 +83,11 @@ cp -r tool/release/fdroid/. "$working/"
 # fdroid refuses a config.yml others can read.
 chmod 600 "$working/config.yml"
 cp snap/gui/halkyon-learn.png "$working/halkyon.png"
+# The app's own icon in the F-Droid app, the same: fdroid can't find the launcher
+# icon in a release APK, whose build shortens the resources' paths (res/9w.png
+# rather than res/mipmap-hdpi/ic_launcher.png; fdroidserver issue 885).
+mkdir -p "$working/metadata/app.halkyon.learn/en-US"
+cp snap/gui/halkyon-learn.png "$working/metadata/app.halkyon.learn/en-US/icon.png"
 if [ -n "$apk" ]; then
   [ -f "$apk" ] || fail "No APK at $apk."
   cp "$apk" "$working/repo/"