♻️(backend) rename convert-markdown endpoint

Renamed the `convert-markdown` endpoint to `convert` as a
general-purpose conversion endpoint for integration with DocSpec
conversion (DOCX import), without altering its existing functionality.

In a future contribution, this endpoint will not only support conversion
from Markdown -> BlockNote -> Yjs but also directly BlockNote -> Yjs.

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

src/backend/impress/settings.py

@@ -639,7 +639,7 @@ class Base(Configuration):
 
     # Conversion endpoint
     CONVERSION_API_ENDPOINT = values.Value(
-        default="convert-markdown",
+        default="convert",
         environ_name="CONVERSION_API_ENDPOINT",
         environ_prefix=None,
     )