feat: implement skills marketplace API with CRUD operations and gateway integration

backend/app/models/gateway_installed_skills.py

@@ -0,0 +1,33 @@
+"""Gateway-to-skill installation state records."""
+
+from __future__ import annotations
+
+from datetime import datetime
+from uuid import UUID, uuid4
+
+from sqlalchemy import UniqueConstraint
+from sqlmodel import Field
+
+from app.core.time import utcnow
+from app.models.base import QueryModel
+
+RUNTIME_ANNOTATION_TYPES = (datetime,)
+
+
+class GatewayInstalledSkill(QueryModel, table=True):
+    """Marks that a marketplace skill is installed for a specific gateway."""
+
+    __tablename__ = "gateway_installed_skills"  # pyright: ignore[reportAssignmentType]
+    __table_args__ = (
+        UniqueConstraint(
+            "gateway_id",
+            "skill_id",
+            name="uq_gateway_installed_skills_gateway_id_skill_id",
+        ),
+    )
+
+    id: UUID = Field(default_factory=uuid4, primary_key=True)
+    gateway_id: UUID = Field(foreign_key="gateways.id", index=True)
+    skill_id: UUID = Field(foreign_key="marketplace_skills.id", index=True)
+    created_at: datetime = Field(default_factory=utcnow)
+    updated_at: datetime = Field(default_factory=utcnow)