fix: apply language filter to --artist searches

When language is configured, --artist now routes through the search
endpoint with 'artist:X language:Y' so results are properly filtered.
Without language set, the faster tagged endpoint is still used.

Closes #435

doujinshi_dl/command.py

@@ -86,6 +86,15 @@ def main():
         )
 
     elif options.artist:
+        if language:
+            logger.info(f'Using default language: {language}')
+            doujinshis = parser.search(
+                f'artist:{options.artist} language:{language}',
+                sorting=options.sorting,
+                page=page_list,
+                is_page_all=options.page_all,
+            )
+        else:
             doujinshis = parser.artist(
                 options.artist,
                 sorting=options.sorting,