feat(android): add Android SDK auto-detection to build-apk.bat

When local.properties is missing, the build script now automatically:
- Checks ANDROID_HOME environment variable first
- Scans common Windows SDK locations:
  - %LOCALAPPDATA%\Android\Sdk
  - %USERPROFILE%\AppData\Local\Android\Sdk
  - C:\Android\Sdk
  - C:\Android
- Creates local.properties with the detected SDK path
- Displays helpful error message if SDK is not found

This allows the build script to work on machines without manual
configuration, making it easier to build APKs on different systems.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/mpc-system/services/service-party-android/build-apk.bat

@@ -14,6 +14,64 @@ if not exist "gradlew.bat" (
     exit /b 1
 )
 
+:: Check and create local.properties if needed
+if not exist "local.properties" (
+    echo [INFO] local.properties not found, attempting to detect Android SDK...
+
+    :: Try common SDK locations
+    set SDK_FOUND=0
+
+    :: Check ANDROID_HOME environment variable first
+    if defined ANDROID_HOME (
+        if exist "!ANDROID_HOME!\platform-tools" (
+            echo sdk.dir=!ANDROID_HOME:\=/!> local.properties
+            echo [INFO] Created local.properties with ANDROID_HOME: !ANDROID_HOME!
+            set SDK_FOUND=1
+        )
+    )
+
+    :: Try common Windows locations
+    if !SDK_FOUND!==0 (
+        for %%P in (
+            "%LOCALAPPDATA%\Android\Sdk"
+            "%USERPROFILE%\AppData\Local\Android\Sdk"
+            "C:\Android\Sdk"
+            "C:\Android"
+            "C:\Users\%USERNAME%\Android\Sdk"
+        ) do (
+            if exist "%%~P\platform-tools" (
+                set "SDK_PATH=%%~P"
+                set "SDK_PATH=!SDK_PATH:\=/!"
+                echo sdk.dir=!SDK_PATH!> local.properties
+                echo [INFO] Created local.properties with SDK path: %%~P
+                set SDK_FOUND=1
+                goto :sdk_found
+            )
+        )
+    )
+
+    :sdk_found
+    if !SDK_FOUND!==0 (
+        echo [ERROR] Android SDK not found!
+        echo.
+        echo Please do one of the following:
+        echo   1. Set ANDROID_HOME environment variable to your SDK path
+        echo   2. Create local.properties file with: sdk.dir=C:/path/to/android/sdk
+        echo   3. Install Android Studio which includes the SDK
+        echo.
+        echo Common SDK locations:
+        echo   - %LOCALAPPDATA%\Android\Sdk
+        echo   - C:\Android\Sdk
+        echo.
+        pause
+        exit /b 1
+    )
+)
+
+echo [INFO] Using SDK from local.properties
+type local.properties
+echo.
+
 :: Parse command line arguments
 set BUILD_TYPE=all
 if "%1"=="debug" set BUILD_TYPE=debug