android: add Tauri v2 shell with GPS tracking for cardio workouts

Wraps the web app in a Tauri Android shell that provides native GPS
via the geolocation plugin. Includes foreground service for background
tracking, live map display, GPS data storage in workout sessions,
and route visualization in workout history.

scripts/android-build-deploy.sh

@@ -0,0 +1,78 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Android SDK environment
+export ANDROID_HOME=/opt/android-sdk
+export NDK_HOME=/opt/android-sdk/ndk/27.0.12077973
+export JAVA_HOME=/usr/lib/jvm/java-21-openjdk
+
+APK_DIR="src-tauri/gen/android/app/build/outputs/apk/universal/release"
+APK_UNSIGNED="$APK_DIR/app-universal-release-unsigned.apk"
+APK_SIGNED="$APK_DIR/app-universal-release-signed.apk"
+KEYSTORE="src-tauri/debug.keystore"
+PACKAGE="org.bocken.fitness"
+
+usage() {
+    echo "Usage: $0 [build|deploy|run]"
+    echo "  build   - Build and sign the APK"
+    echo "  deploy  - Build + install on connected device"
+    echo "  run     - Build + install + launch on device"
+    exit 1
+}
+
+ensure_keystore() {
+    if [ ! -f "$KEYSTORE" ]; then
+        echo ":: Generating debug keystore..."
+        keytool -genkey -v -keystore "$KEYSTORE" \
+            -alias debug -keyalg RSA -keysize 2048 -validity 10000 \
+            -storepass android -keypass android \
+            -dname "CN=Debug,O=Bocken,C=DE"
+    fi
+}
+
+build() {
+    echo ":: Building Android APK..."
+    npx tauri android build --apk
+
+    ensure_keystore
+
+    echo ":: Signing APK..."
+    # zipalign
+    "$ANDROID_HOME/build-tools/35.0.0/zipalign" -f -v 4 \
+        "$APK_UNSIGNED" "$APK_SIGNED" > /dev/null
+
+    # sign with apksigner
+    "$ANDROID_HOME/build-tools/35.0.0/apksigner" sign \
+        --ks "$KEYSTORE" --ks-pass pass:android --key-pass pass:android \
+        "$APK_SIGNED"
+
+    echo ":: Signed APK at: $APK_SIGNED"
+}
+
+deploy() {
+    if ! adb devices | grep -q "device$"; then
+        echo "!! No device connected. Connect your phone and enable USB debugging."
+        exit 1
+    fi
+
+    build
+
+    echo ":: Installing APK on device..."
+    adb install -r "$APK_SIGNED"
+    echo ":: Installed successfully."
+}
+
+run() {
+    deploy
+
+    echo ":: Launching app..."
+    adb shell am start -n "$PACKAGE/.MainActivity"
+    echo ":: App launched."
+}
+
+case "${1:-}" in
+    build)  build ;;
+    deploy) deploy ;;
+    run)    run ;;
+    *)      usage ;;
+esac