Use port 8757 for the dev server

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.devcontainer/devcontainer.json

@@ -17,6 +17,6 @@
     },
     "postCreateCommand": "pip install -U pip && pip install -U -r requirements.txt -r requirements-dev.txt",
     "forwardPorts": [
-        8000
+        8757
     ]
 }