fix(proxy): use internal container port instead of host port

The proxy was using instance.port which is a dynamically allocated
host port (e.g., 10001). But containers communicate on the Docker
network using their internal ports (8443 for code-server, 8888 for
jupyter). This caused connection failures when opening instances.

- Add default_port field to ToolType model (null for terminal-only tools)
- Create migration 0010 for default_port column
- Update seed data: code-server=8443, jupyter=8888, opencode=null
- Update proxy to use tool type's default_port instead of instance.port
- Update frontend ToolType interface to include default_port

Fixes: Opening instances now routes to correct internal container port

apps/api/src/main.py

@@ -123,6 +123,7 @@ services:
     ports:
       - "8443:8443"
     restart: unless-stopped""",
+                "default_port": 8443,
                 "required_variables": ["REPO_PATH", "TOOL_NAME"],
             },
             {
@@ -131,6 +132,7 @@ services:
                 "description": "Jupyter Lab for interactive development",
                 "category": "notebook",
                 "interfaces": ["web"],
+                "default_port": 8888,
                 "compose_template": """version: "3.8"
 services:
   jupyter:
@@ -187,6 +189,7 @@ volumes:
                     interfaces=tool_data["interfaces"],
                     compose_template=tool_data["compose_template"],
                     required_variables=tool_data["required_variables"],
+                    default_port=tool_data.get("default_port"),
                     is_builtin=True,
                 )
                 session.add(tool_type)