refactor: consolidate sandbox management and initialization

- Moved sandbox-related classes and functions into a dedicated module for better organization.
- Updated the sandbox initialization process to streamline asset management and environment setup.
- Removed deprecated constants and refactored related code to utilize new sandbox entities.
- Enhanced the workflow context to support sandbox integration, allowing for improved state management during execution.
- Adjusted various components to utilize the new sandbox structure, ensuring compatibility across the application.

api/core/workflow/context/__init__.py

@@ -17,7 +17,6 @@ from core.workflow.context.execution_context import (
     register_context_capturer,
     reset_context_provider,
 )
-from core.workflow.context.models import SandboxContext
 
 __all__ = [
     "AppContext",
@@ -25,7 +24,6 @@ __all__ = [
     "ExecutionContext",
     "IExecutionContext",
     "NullAppContext",
-    "SandboxContext",
     "capture_current_context",
     "read_context",
     "register_context",

api/core/workflow/context/models.py

@@ -1,13 +1,3 @@
 from __future__ import annotations
 
-from pydantic import AnyHttpUrl, BaseModel
-
-
-class SandboxContext(BaseModel):
-    """Typed context for sandbox integration. All fields optional by design."""
-
-    sandbox_url: AnyHttpUrl | None = None
-    sandbox_token: str | None = None  # optional, if later needed for auth
-
-
-__all__ = ["SandboxContext"]
+__all__: list[str] = []