feat(phase-24): integrate MITRE D3FEND defensive techniques with ATT&CK mapping (T-213, T-214)

backend/app/models/defensive_technique.py

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+"""DefensiveTechnique and DefensiveTechniqueMapping models.
+
+Stores MITRE D3FEND defensive techniques and their mappings to
+ATT&CK techniques, enabling recommended countermeasure lookups.
+"""
+
+import uuid
+from datetime import datetime
+
+from sqlalchemy import (
+    Column, String, Text, DateTime,
+    ForeignKey, Index, UniqueConstraint,
+)
+from sqlalchemy.dialects.postgresql import UUID
+from sqlalchemy.orm import relationship
+
+from app.database import Base
+
+
+class DefensiveTechnique(Base):
+    """
+    MITRE D3FEND defensive technique.
+
+    Represents a countermeasure from the D3FEND framework that can be
+    mapped to one or more ATT&CK techniques via DefensiveTechniqueMapping.
+    """
+    __tablename__ = "defensive_techniques"
+
+    id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    d3fend_id = Column(String, unique=True, nullable=False)          # e.g. "D3-AL"
+    name = Column(String, nullable=False)
+    description = Column(Text, nullable=True)
+    tactic = Column(String, nullable=True)                            # Detect, Isolate, Deceive, Evict, etc.
+    d3fend_url = Column(String, nullable=True)
+    created_at = Column(DateTime, default=datetime.utcnow)
+
+    # Relationships
+    attack_mappings = relationship(
+        "DefensiveTechniqueMapping",
+        back_populates="defensive_technique",
+        cascade="all, delete-orphan",
+    )
+
+    __table_args__ = (
+        Index('ix_defensive_techniques_tactic', 'tactic'),
+    )
+
+
+class DefensiveTechniqueMapping(Base):
+    """
+    Association between a MITRE ATT&CK technique and a D3FEND
+    defensive technique.
+    """
+    __tablename__ = "defensive_technique_mappings"
+
+    id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    attack_technique_id = Column(
+        UUID(as_uuid=True),
+        ForeignKey("techniques.id", ondelete="CASCADE"),
+        nullable=False,
+    )
+    defensive_technique_id = Column(
+        UUID(as_uuid=True),
+        ForeignKey("defensive_techniques.id", ondelete="CASCADE"),
+        nullable=False,
+    )
+
+    # Relationships
+    attack_technique = relationship("Technique")
+    defensive_technique = relationship("DefensiveTechnique", back_populates="attack_mappings")
+
+    __table_args__ = (
+        Index('ix_dtm_attack_technique', 'attack_technique_id'),
+        Index('ix_dtm_defensive_technique', 'defensive_technique_id'),
+        UniqueConstraint(
+            'attack_technique_id', 'defensive_technique_id',
+            name='uq_attack_defensive_technique',
+        ),
+    )