feat(fase4): add GlobalVariable database model

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

services/api-gateway/app/models/global_variable.py

@@ -0,0 +1,18 @@
+import uuid
+from datetime import datetime
+from sqlalchemy import Column, String, Text, DateTime, Boolean
+from sqlalchemy.dialects.postgresql import UUID
+from app.core.database import Base
+
+
+class GlobalVariable(Base):
+    __tablename__ = "global_variables"
+
+    id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    key = Column(String(100), nullable=False, unique=True, index=True)
+    value = Column(Text, nullable=True)
+    value_type = Column(String(20), default="string", nullable=False)
+    description = Column(String(500), nullable=True)
+    is_secret = Column(Boolean, default=False, nullable=False)
+    created_at = Column(DateTime, default=datetime.utcnow, nullable=False)
+    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False)