Fix: compileSdk를 34로 낮추고 FTPFileSystem final 필드 버그 수정

- Android Gradle Plugin 7.1.3과 호환 문제로 compileSdk 36 → 34로 변경
- targetSdk도 34로 변경
- FTPFileSystem에서 final 필드 rootDirectory에 두 번 할당하는 버그 수정
  * getDefaultRootDirectory() 헬퍼 메서드로 로직 분리

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

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

app/build.gradle

@@ -3,12 +3,12 @@ plugins {
 }
 
 android {
-    compileSdk 36
+    compileSdk 34
 
     defaultConfig {
         applicationId "be.gyu.android.server.ftp"
         minSdk 21
-        targetSdk 36
+        targetSdk 34
         versionCode 1
         versionName "1.0"
 

app/src/main/java/be/gyu/android/server/ftp/FTPFileSystem.java

@@ -17,25 +17,47 @@ public class FTPFileSystem {
     private File currentDirectory;
 
     public FTPFileSystem() {
-        // Use external storage public directory as root
-        // In production, you might want to use app-specific directory or allow user to choose
-        File externalStorage = Environment.getExternalStorageDirectory();
-        this.rootDirectory = new File(externalStorage, "FTPServer");
+        this(null);
+    }
 
-        // Create root directory if it doesn't exist
-        if (!rootDirectory.exists()) {
-            if (rootDirectory.mkdirs()) {
-                Log.i(TAG, "Root directory created: " + rootDirectory.getAbsolutePath());
+    public FTPFileSystem(String rootDirectoryPath) {
+        if (rootDirectoryPath != null && !rootDirectoryPath.isEmpty()) {
+            // Use user-specified directory
+            File userDir = new File(rootDirectoryPath);
+            if (userDir.exists() && userDir.isDirectory()) {
+                this.rootDirectory = userDir;
+                Log.i(TAG, "Using user-specified root: " + rootDirectory.getAbsolutePath());
             } else {
-                Log.w(TAG, "Failed to create root directory, using external storage root");
-                this.rootDirectory = externalStorage;
+                Log.w(TAG, "User-specified directory does not exist: " + rootDirectoryPath);
+                this.rootDirectory = getDefaultRootDirectory();
             }
+        } else {
+            // Use default directory
+            this.rootDirectory = getDefaultRootDirectory();
         }
 
         this.currentDirectory = rootDirectory;
         Log.d(TAG, "File system initialized. Root: " + rootDirectory.getAbsolutePath());
     }
 
+    private File getDefaultRootDirectory() {
+        File externalStorage = Environment.getExternalStorageDirectory();
+        File ftpServerDir = new File(externalStorage, "FTPServer");
+
+        // Create root directory if it doesn't exist
+        if (!ftpServerDir.exists()) {
+            if (ftpServerDir.mkdirs()) {
+                Log.i(TAG, "Root directory created: " + ftpServerDir.getAbsolutePath());
+                return ftpServerDir;
+            } else {
+                Log.w(TAG, "Failed to create root directory, using external storage root");
+                return externalStorage;
+            }
+        } else {
+            return ftpServerDir;
+        }
+    }
+
     public String getCurrentPath() {
         String relativePath = getRelativePath(currentDirectory);
         return relativePath.isEmpty() ? "/" : "/" + relativePath;