feat: implement tool workshop - comprehensive tool system enhancement

- Add Docker Compose and Dockerfile support for tool definitions
- Implement readiness probes with configurable command, timeout, interval
- Create ConfigFolder model for reusable file collections with project overrides
- Add rich tool config fields: port_override, start_command, working_directory, env vars, volumes
- Build unified Tool Workshop UI at /tool-workshop replacing /tool-configs and /tool-types
- Update instance creation to support dockerfile builds, config folder mounting, readiness probes
- Add 3 database migrations for tool_types, tool_configs, and new config_folders table
- Create docker_build.py and readiness_probe.py services
- Add config_folders API with CRUD and project override endpoints

Quality gates: frontend build passes, Python syntax valid, all phases complete

Addresses tool-workshop OpenSpec change

apps/api/src/models/__init__.py

@@ -1,4 +1,5 @@
 from src.models.base import Base
+from src.models.config_folder import ConfigFolder
 from src.models.git_repository import GitRepository
 from src.models.project import Project
 from src.models.ssh_key import SSHKey
@@ -7,4 +8,4 @@ from src.models.tool_type import ToolType
 from src.models.user import User
 from src.models.user_config import UserConfig
 
-__all__ = ["Base", "GitRepository", "Project", "SSHKey", "ToolInstance", "ToolType", "User", "UserConfig"]
+__all__ = ["Base", "ConfigFolder", "GitRepository", "Project", "SSHKey", "ToolInstance", "ToolType", "User", "UserConfig"]