Fixed the problem that copying the default theme at halo startup did not use...

Fixed the problem that copying the default theme at halo startup did not use themeId as the theme folder name (#1549)

* fix: 1547

* refactor: replace the string magic value using a static constant

src/main/java/run/halo/app/listener/StartedListener.java

@@ -165,10 +165,10 @@ public class StartedListener implements ApplicationListener<ApplicationStartedEv
             }
 
             // Create theme folder
-            Path themePath = themeService.getBasePath();
+            Path themePath = themeService.getBasePath().resolve(HaloConst.DEFAULT_THEME_ID);
 
             if (themeService.fetchThemePropertyBy(HaloConst.DEFAULT_THEME_ID).isEmpty()) {
-                FileUtils.copyFolder(source, themePath);
+                FileUtils.copyFolder(source.resolve(HaloConst.DEFAULT_THEME_DIR_NAME), themePath);
                 log.info("Copied theme folder from [{}] to [{}]", source, themePath);
             }
         } catch (Exception e) {

src/main/java/run/halo/app/model/support/HaloConst.java

@@ -48,6 +48,11 @@ public class HaloConst {
      */
     public static final String DEFAULT_THEME_ID = "caicai_anatole";
 
+    /**
+     * Default theme directory name.
+     */
+    public static final String DEFAULT_THEME_DIR_NAME = "anatole";
+
     /**
      * Default error path.
      */