Add a custom Android CI/release build image and packaging scripts

- build-image/: Dockerfile bundling JDK 17, the Android SDK, and
  Node.js (needed by Gitea's JS-based actions) - the app has no
  native code, so no NDK
- build-image.sh/upload-image.sh: extended to also build/push this
  image alongside the existing OCR pipeline tools image
- run-image.sh: runs `make android` inside the image against a live
  checkout, for a CI-equivalent local build
- Makefile: `make android` builds and versions a release APK into
  dist/, from the current git tag
- .gitea/workflows/build.yml: now pulls the custom image and just
  runs `make android`, replacing the ad-hoc Node/SDK install steps
- README.md: describes the pipeline, server, app, and build tooling
- registry.env.example: fix REGISTRY_IMAGE to be fully-qualified
  (an unqualified name was silently resolving pushes to Docker Hub
  instead of the configured registry)

upload-image.sh

@@ -1,8 +1,10 @@
 #!/usr/bin/env bash
-# Pushes the fuelish tools image - already built locally with
-# ./build-image.sh, and ideally verified with the numbered pipeline
-# scripts - to a container registry, so the k3s cluster (or other
-# machines) can pull it without rebuilding it.
+# Pushes every image ./build-image.sh built locally - the fuelish tools
+# image and the Android CI/release build image, each already verified
+# (tools image with the numbered pipeline scripts, android-builder image
+# with ./run-image.sh) - to a container registry, so the k3s cluster can
+# pull the tools image and Gitea Actions can pull the android-builder
+# image without rebuilding either.
 set -euo pipefail
 
 cd "$(dirname "${BASH_SOURCE[0]}")"
@@ -21,21 +23,31 @@ source "$ROOT/registry.env"
 
 : "${REGISTRY:?registry.env must set REGISTRY}"
 : "${REGISTRY_IMAGE:?registry.env must set REGISTRY_IMAGE}"
+: "${REGISTRY_ANDROID_IMAGE:?registry.env must set REGISTRY_ANDROID_IMAGE}"
 : "${REGISTRY_USER:?registry.env must set REGISTRY_USER}"
 : "${REGISTRY_PASSWORD:?registry.env must set REGISTRY_PASSWORD}"
 
-VERSION="$(<"$ROOT/tooling-container/VERSION")"
-[ -n "$VERSION" ] || fail "tooling-container/VERSION is empty"
+TOOLS_VERSION="$(<"$ROOT/tooling-container/VERSION")"
+[ -n "$TOOLS_VERSION" ] || fail "tooling-container/VERSION is empty"
 
-docker image inspect "$REGISTRY_IMAGE:$VERSION" >/dev/null 2>&1 \
-    || fail "$REGISTRY_IMAGE:$VERSION not found locally - run ./build-image.sh first"
+ANDROID_VERSION="$(<"$ROOT/build-image/VERSION")"
+[ -n "$ANDROID_VERSION" ] || fail "build-image/VERSION is empty"
+
+docker image inspect "$REGISTRY_IMAGE:$TOOLS_VERSION" >/dev/null 2>&1 \
+    || fail "$REGISTRY_IMAGE:$TOOLS_VERSION not found locally - run ./build-image.sh first"
+docker image inspect "$REGISTRY_ANDROID_IMAGE:$ANDROID_VERSION" >/dev/null 2>&1 \
+    || fail "$REGISTRY_ANDROID_IMAGE:$ANDROID_VERSION not found locally - run ./build-image.sh first"
 
 echo "== Logging in to $REGISTRY =="
 echo "$REGISTRY_PASSWORD" | docker login "$REGISTRY" -u "$REGISTRY_USER" --password-stdin
 
-echo "== Pushing $REGISTRY_IMAGE:$VERSION and :latest =="
-docker push "$REGISTRY_IMAGE:$VERSION"
+echo "== Pushing $REGISTRY_IMAGE:$TOOLS_VERSION and :latest =="
+docker push "$REGISTRY_IMAGE:$TOOLS_VERSION"
 docker push "$REGISTRY_IMAGE:latest"
 
+echo "== Pushing $REGISTRY_ANDROID_IMAGE:$ANDROID_VERSION and :latest =="
+docker push "$REGISTRY_ANDROID_IMAGE:$ANDROID_VERSION"
+docker push "$REGISTRY_ANDROID_IMAGE:latest"
+
 echo "== Done =="
-echo "Image: $REGISTRY_IMAGE:$VERSION"
+echo "Images: $REGISTRY_IMAGE:$TOOLS_VERSION, $REGISTRY_ANDROID_IMAGE:$ANDROID_VERSION"