fix: correct LM Studio URL parsing and uvicorn port binding (fixes #394)

- lm_studio_fn: use urlparse to extract port from server_address so that
  addresses with an http:// prefix (e.g. http://127.0.0.1:1234, as
  documented in README) no longer break the Docker URL construction.
  Previously split(":")[1] returned "//127.0.0.1" instead of the port
  number, producing a malformed URL.
  Also fix the non-Docker path to avoid prepending http:// when the address
  already includes a scheme.

- api.py: pass the computed port variable to uvicorn.run() instead of the
  hardcoded literal 7777, so that BACKEND_PORT environment variable is
  actually honoured when starting the server directly.

api.py

@@ -299,4 +299,4 @@ if __name__ == "__main__":
         port = int(envport)
     else:
         port = 7777
-    uvicorn.run(api, host="0.0.0.0", port=7777)
+    uvicorn.run(api, host="0.0.0.0", port=port)