♻️(backend) rename convert_markdown to convert (#1114)

Renamed the `convert_markdown` method to `convert` to prepare for an
all-purpose conversion endpoint, enabling support for multiple formats
and simplifying future extension.

Signed-off-by: Stephan Meijer <me@stephanmeijer.com>

src/backend/core/services/converter_services.py

@@ -34,7 +34,7 @@ class YdocConverter:
         # Note: Yprovider microservice accepts only raw token, which is not recommended
         return settings.Y_PROVIDER_API_KEY
 
-    def convert_markdown(self, text):
+    def convert(self, text):
         """Convert a Markdown text into our internal format using an external microservice."""
 
         if not text: