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/config_folder.py

@@ -0,0 +1,31 @@
+import uuid
+from typing import TYPE_CHECKING
+
+from sqlalchemy import Boolean, ForeignKey, JSON, String, Text
+from sqlalchemy import Uuid as UUID
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from src.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
+
+if TYPE_CHECKING:
+    from src.models.user import User
+
+
+class ConfigFolder(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+    __tablename__ = "config_folders"
+
+    user_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(), ForeignKey("users.id", ondelete="CASCADE"), nullable=False
+    )
+    name: Mapped[str] = mapped_column(String(255), nullable=False)
+    description: Mapped[str | None] = mapped_column(Text, nullable=True)
+    mount_path: Mapped[str] = mapped_column(String(1024), nullable=False)
+    files: Mapped[dict] = mapped_column(
+        JSON, default=dict, nullable=False
+    )  # {"relative/path": "content", ...}
+    project_overrides: Mapped[dict | None] = mapped_column(
+        JSON, default=dict, nullable=True
+    )  # {"project_id": {"mount_path": "...", "files": {...}}}
+    is_active: Mapped[bool] = mapped_column(Boolean, default=True, nullable=False)
+
+    user: Mapped["User"] = relationship()