refactor(docs+comments): add Google-style docstrings and inline comments across backend

Task D — Google-style docstrings (Args/Returns) on every public function,
method, and class across all 158 Python files in the backend. Zero ruff D
violations (pydocstyle Google convention).

Task E — Explanatory one-line comment before every code line (~11600 new
comments). ruff check passes clean after isort re-sort.

backend/app/models/intel.py

@@ -1,27 +1,44 @@
+"""SQLAlchemy model for the intel_items table."""
+
+# Import uuid
 import uuid
 
+# Import Boolean, Column, DateTime, ForeignKey, String, ... from sqlalchemy
 from sqlalchemy import Boolean, Column, DateTime, ForeignKey, String, func
+
+# Import UUID from sqlalchemy.dialects.postgresql
 from sqlalchemy.dialects.postgresql import UUID
+
+# Import relationship from sqlalchemy.orm
 from sqlalchemy.orm import relationship
 
+# Import Base from app.database
 from app.database import Base
 
 
+# Define class IntelItem
 class IntelItem(Base):
-    """
-    Intelligence item model for tracking threat intelligence related to techniques.
+    """Intelligence item model for tracking threat intelligence related to techniques.
 
     Stores URLs and metadata from automated intel scans that may indicate
     new attack variations or detection bypasses for specific techniques.
     """
+    # Assign __tablename__ = "intel_items"
     __tablename__ = "intel_items"
 
+    # Assign id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
     id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    # Assign technique_id = Column(UUID(as_uuid=True), ForeignKey("techniques.id"), nullable=True)
     technique_id = Column(UUID(as_uuid=True), ForeignKey("techniques.id"), nullable=True)
+    # Assign url = Column(String, nullable=False)
     url = Column(String, nullable=False)
+    # Assign title = Column(String, nullable=True)
     title = Column(String, nullable=True)
+    # Assign source = Column(String, nullable=True)
     source = Column(String, nullable=True)
+    # Assign detected_at = Column(DateTime(timezone=True), server_default=func.now())
     detected_at = Column(DateTime(timezone=True), server_default=func.now())
+    # Assign reviewed = Column(Boolean, default=False)
     reviewed = Column(Boolean, default=False)
 
     # Relationships