feat: add survey_invites migration and invite_id FK

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/models/survey_response.py

@@ -0,0 +1,20 @@
+"""FlowPilot survey response storage."""
+import uuid
+from datetime import datetime, timezone
+
+from sqlalchemy import Column, DateTime, ForeignKey, String, Text
+from sqlalchemy.dialects.postgresql import JSONB, UUID
+
+from app.core.database import Base
+
+
+class SurveyResponse(Base):
+    __tablename__ = "survey_responses"
+
+    id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    respondent_name = Column(String(255), nullable=True)
+    responses = Column(JSONB, nullable=False)
+    ip_address = Column(String(45), nullable=True)
+    user_agent = Column(Text, nullable=True)
+    invite_id = Column(UUID(as_uuid=True), ForeignKey("survey_invites.id"), nullable=True)
+    created_at = Column(DateTime(timezone=True), default=lambda: datetime.now(timezone.utc), nullable=False)