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/models/tool_type.py

@@ -19,6 +19,7 @@ class ToolType(UUIDPrimaryKeyMixin, TimestampMixin, Base):
     description: Mapped[str | None] = mapped_column(Text, nullable=True)
     category: Mapped[str] = mapped_column(String(50), nullable=False, default="other")
     interfaces: Mapped[list[str]] = mapped_column(JSON, default=list, nullable=False)
+    default_port: Mapped[int | None] = mapped_column(nullable=True)
     compose_template: Mapped[str] = mapped_column(Text, nullable=False)
     required_variables: Mapped[list[str]] = mapped_column(JSON, default=list, nullable=False)
     is_builtin: Mapped[bool] = mapped_column(Boolean, default=False, nullable=False)