Add a standalone Android app with the same daily reading and config page

android/ links engine/src/ and interpreter/src/ via JNI/CMake (real
astronomy.c, not the watch's size-constrained substitute), rendering
through Jetpack Compose with a burger-menu config page mirroring
WatchConfig and a WorkManager-driven daily notification. Independent
of the watch app - neither requires the other.

build-image now bundles the Android SDK/NDK alongside the Pebble SDK
(VERSION bumped to 2), and .gitea/workflows/build.yml/Makefile/
run-image.sh build and publish the APK the same way as the CLI
tarball and .pbw.

build-image/Dockerfile

@@ -1,7 +1,8 @@
 # Build environment for deck_in_a_dash release artifacts: a plain C
 # toolchain for the desktop deck-engine/interpreter-cli binaries (`make
-# test`, `make package`) plus the Pebble SDK for the watch app (`make
-# watchapp`), pinned to the versions validated on the maintainer's dev
+# test`, `make package`), the Pebble SDK for the watch app (`make
+# watchapp`), and the Android SDK/NDK for the Android app (`make
+# android`), pinned to the versions validated on the maintainer's dev
 # machine. Rebuild with ../build-image.sh whenever a version below
 # changes.
 #
@@ -12,17 +13,28 @@ FROM ubuntu:22.04
 ARG PEBBLE_TOOL_VERSION=5.0.39
 ARG PEBBLE_SDK_CORE_VERSION=4.17
 ARG NODE_VERSION=24.16.0
+ARG ANDROID_CMDLINE_TOOLS_VERSION=9862592
+ARG ANDROID_PLATFORM_VERSION=36
+ARG ANDROID_BUILD_TOOLS_VERSION=36.0.0
+ARG ANDROID_NDK_VERSION=30.0.14904198
+ARG ANDROID_CMAKE_VERSION=3.22.1
 
 ENV DEBIAN_FRONTEND=noninteractive \
     PATH=/root/.local/bin:${PATH}
 
 # build-essential: gcc/make for the desktop deck-engine/interpreter-cli
-# binaries (`make test`, `make package`).
+# binaries (`make test`, `make package`) and for the Android app's JNI
+# native library (app/src/main/jni/CMakeLists.txt - the NDK's own
+# toolchain does the actual cross-compiling, but AGP's build needs a
+# host C toolchain available too).
 # python3/python3-venv/python3-pip: `pebble sdk install` below creates a
 # venv per SDK version; Pillow (installed below) is needed at `pebble
-# build` time by watch/scripts/gen_card_images.py and gen_app_icon.py.
+# build` time by watch/scripts/gen_card_images.py and gen_app_icon.py,
+# and by the Android app's android/scripts/gen_card_images.py and
+# gen_launcher_icon.py.
 # git/curl/ca-certificates/unzip/tar/xz-utils: checkout, tool downloads,
-# and `make package`/`make watchapp`'s `git describe --tags` versioning.
+# and `make package`/`make watchapp`/`make android`'s `git describe
+# --tags` versioning.
 # openssh-client: the build workflow's `sftp` publish to dl.ladkau.de.
 RUN apt-get update && apt-get install -y --no-install-recommends \
         build-essential python3 python3-venv python3-pip \
@@ -46,4 +58,37 @@ RUN curl -LsSf https://astral.sh/uv/install.sh | sh \
     && uv tool install "pebble-tool==${PEBBLE_TOOL_VERSION}" \
     && pebble sdk install "${PEBBLE_SDK_CORE_VERSION}"
 
+# Android SDK/NDK: openjdk-17 (Gradle/AGP's own minimum JDK) + the
+# cmdline-tools' own sdkmanager to install exactly the platform/build-
+# tools/NDK/CMake versions android/app/build.gradle.kts pins - unlike
+# the Pebble/CLI build path above, `make android`'s own Gradle build
+# still needs network access at build time (Gradle/AGP/androidx
+# dependency resolution against Google's Maven + Maven Central - see the
+# root CLAUDE.md's Android section for why this is an accepted,
+# deliberate deviation from this image's otherwise-offline build
+# philosophy). android/gradlew resolves its own pinned Gradle version -
+# no Gradle binary is baked into this image.
+RUN apt-get update && apt-get install -y --no-install-recommends openjdk-17-jdk-headless \
+    && rm -rf /var/lib/apt/lists/*
+
+ENV ANDROID_HOME=/opt/android-sdk \
+    ANDROID_SDK_ROOT=/opt/android-sdk
+ENV PATH=${ANDROID_HOME}/cmdline-tools/latest/bin:${ANDROID_HOME}/platform-tools:${PATH}
+
+RUN mkdir -p "${ANDROID_HOME}/cmdline-tools" \
+    && curl -sSL -o /tmp/cmdline-tools.zip \
+        "https://dl.google.com/android/repository/commandlinetools-linux-${ANDROID_CMDLINE_TOOLS_VERSION}_latest.zip" \
+    && unzip -q /tmp/cmdline-tools.zip -d "${ANDROID_HOME}/cmdline-tools" \
+    && mv "${ANDROID_HOME}/cmdline-tools/cmdline-tools" "${ANDROID_HOME}/cmdline-tools/latest" \
+    && rm /tmp/cmdline-tools.zip \
+    && yes | sdkmanager --licenses >/dev/null \
+    && sdkmanager --install \
+        "platform-tools" \
+        "platforms;android-${ANDROID_PLATFORM_VERSION}" \
+        "build-tools;${ANDROID_BUILD_TOOLS_VERSION}" \
+        "ndk;${ANDROID_NDK_VERSION}" \
+        "cmake;${ANDROID_CMAKE_VERSION}"
+
+ENV ANDROID_NDK_HOME=${ANDROID_HOME}/ndk/${ANDROID_NDK_VERSION}
+
 WORKDIR /workspace