Fix Kobo sync downloading incorrect books due to stale temp files

The Kobo sync process was occasionally serving the wrong book content because of unsafe file handling in the temporary directory used for metadata embedding.

- Fixed `do_calibre_export` in `cps/embed_helper.py` to strictly match the requested filename (UUID) instead of returning the first file found with the correct extension.
- Added cleanup logic to `_convert_kepubify` in `cps/tasks/convert.py` to ensure temporary source files are deleted after conversion, preventing the accumulationFix Kobo sync downloading incorrect books due to stale temp files

The Kobo sync process was occasionally serving the wrong book content because of unsafe file handling in the temporary directory used for metadata embedding.

- Fixed `do_calibre_export` in `cps/embed_helper.py` to strictly match the requested filename (UUID) instead of returning the first file found with the correct extension.
- Added cleanup logic to `_convert_kepubify` in `cps/tasks/convert.py` to ensure temporary source files are deleted after conversion, preventing the accumulation of stale files.

This resolves the issue where multiple different books would download as the same book content on Kobo devices.

Author: crocodilestick

cps/embed_helper.py

@@ -51,12 +51,14 @@ def do_calibre_export(book_id, book_format):
             log.warning(f'No {book_format} file found in export directory: {export_dir}')
         else:
             # No subdirectory - look for files directly in tmp_dir
+            # STRICT CHECK: Only look for the file we requested
+            expected_filename = temp_file_name + '.' + book_format.lower()
             for filename in os.listdir(tmp_dir):
-                if filename.lower().endswith('.' + book_format.lower()):
+                if filename.lower() == expected_filename.lower():
                     actual_filename = os.path.splitext(filename)[0]
                     return tmp_dir, actual_filename
 
-            log.warning(f'No {book_format} file found in {tmp_dir}')
+            log.warning(f'No file named {expected_filename} found in {tmp_dir}')
 
         # Fallback to original behavior
         return tmp_dir, temp_file_name

cps/tasks/convert.py

@@ -236,8 +236,19 @@ def _convert_kepubify(self, file_path, format_old_ext, format_new_ext):
                 copyfile(converted_file[0], (file_path + format_new_ext))
                 os.unlink(converted_file[0])
             else:
+                if config.config_embed_metadata and config.config_binariesdir and os.path.isfile(filename):
+                    try:
+                        os.remove(filename)
+                    except OSError:
+                        pass
                 return 1, N_("Converted file not found or more than one file in folder %(folder)s",
                              folder=os.path.dirname(file_path))
+
+        if config.config_embed_metadata and config.config_binariesdir and os.path.isfile(filename):
+            try:
+                os.remove(filename)
+            except OSError:
+                pass
         return check, None
 
     def _convert_calibre(self, file_path, format_old_ext, format_new_ext, has_cover):