fix(android): properly handle GOPATH/bin for gomobile in build-apk.bat

Changes:
- Get GOPATH using 'go env GOPATH' command
- Add GOPATH/bin to PATH if not already present
- Check for gomobile.exe directly in GOBIN directory
- Use full path to gomobile.exe for init and bind commands
- Add verification that gomobile was installed correctly

This fixes the issue where gomobile is installed but not found
because GOPATH/bin is not in the system PATH.

🤖 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

@@ -89,18 +89,46 @@ if not exist "app\libs\tsslib.aar" (
         exit /b 1
     )
 
+    :: Get GOPATH for bin directory
+    for /f "tokens=*" %%G in ('go env GOPATH') do set "GOPATH_DIR=%%G"
+    if not defined GOPATH_DIR set "GOPATH_DIR=%USERPROFILE%\go"
+    set "GOBIN_DIR=!GOPATH_DIR!\bin"
+
+    :: Add GOPATH/bin to PATH if not already there
+    echo !PATH! | findstr /i /c:"!GOBIN_DIR!" >nul 2>nul
+    if !errorlevel! neq 0 (
+        echo [INFO] Adding !GOBIN_DIR! to PATH...
+        set "PATH=!PATH!;!GOBIN_DIR!"
+    )
+
     :: Check if gomobile is installed
     where gomobile >nul 2>nul
     if !errorlevel! neq 0 (
-        echo [INFO] gomobile not found, installing...
-        go install golang.org/x/mobile/cmd/gomobile@latest
-        if !errorlevel! neq 0 (
-            echo [ERROR] Failed to install gomobile!
+        :: Also check in GOBIN directly
+        if not exist "!GOBIN_DIR!\gomobile.exe" (
+            echo [INFO] gomobile not found, installing...
+            go install golang.org/x/mobile/cmd/gomobile@latest
+            if !errorlevel! neq 0 (
+                echo [ERROR] Failed to install gomobile!
+                pause
+                exit /b 1
+            )
+        )
+
+        :: Verify gomobile exists after install
+        if not exist "!GOBIN_DIR!\gomobile.exe" (
+            echo [ERROR] gomobile was not installed correctly!
+            echo Please check your Go installation and GOPATH.
+            echo Expected location: !GOBIN_DIR!\gomobile.exe
             pause
             exit /b 1
         )
-        :: Initialize gomobile
-        gomobile init
+
+        echo [INFO] Initializing gomobile...
+        "!GOBIN_DIR!\gomobile.exe" init
+        if !errorlevel! neq 0 (
+            echo [WARNING] gomobile init failed, but continuing...
+        )
     )
 
     :: Get the tsslib directory path (relative to service-party-android)
@@ -125,8 +153,8 @@ if not exist "app\libs\tsslib.aar" (
         exit /b 1
     )
 
-    :: Build the AAR
-    gomobile bind -target=android -o "..\..\services\service-party-android\app\libs\tsslib.aar" .
+    :: Build the AAR (use full path to gomobile)
+    "!GOBIN_DIR!\gomobile.exe" bind -target=android -o "..\..\services\service-party-android\app\libs\tsslib.aar" .
     if !errorlevel! neq 0 (
         echo [ERROR] gomobile bind failed!
         popd