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/jira_link.py

@@ -1,55 +1,99 @@
 """Jira integration models — link Aegis entities to Jira issues."""
 
+# Import enum
 import enum
+
+# Import uuid
 import uuid
 
+# Import Column, DateTime, ForeignKey, Index, String, func from sqlalchemy
 from sqlalchemy import Column, DateTime, ForeignKey, Index, String, func
+
+# Import Enum as SQLEnum from sqlalchemy
 from sqlalchemy import Enum as SQLEnum
+
+# Import JSONB, UUID from sqlalchemy.dialects.postgresql
 from sqlalchemy.dialects.postgresql import JSONB, UUID
+
+# Import relationship from sqlalchemy.orm
 from sqlalchemy.orm import relationship
 
+# Import Base from app.database
 from app.database import Base
 
 
+# Define class JiraLinkEntityType
 class JiraLinkEntityType(str, enum.Enum):
+    """Aegis entity types that can be linked to a Jira issue."""
+
+    # Assign test = "test"
     test = "test"
+    # Assign technique = "technique"
     technique = "technique"
+    # Assign campaign = "campaign"
     campaign = "campaign"
+    # Assign evidence = "evidence"
     evidence = "evidence"
 
 
+# Define class JiraSyncDirection
 class JiraSyncDirection(str, enum.Enum):
+    """Direction of synchronisation between Aegis and Jira."""
+
+    # Assign aegis_to_jira = "aegis_to_jira"
     aegis_to_jira = "aegis_to_jira"
+    # Assign jira_to_aegis = "jira_to_aegis"
     jira_to_aegis = "jira_to_aegis"
+    # Assign bidirectional = "bidirectional"
     bidirectional = "bidirectional"
 
 
+# Define class JiraLink
 class JiraLink(Base):
     """Associates an Aegis entity with a Jira issue for bidirectional sync."""
 
+    # Assign __tablename__ = "jira_links"
     __tablename__ = "jira_links"
 
+    # 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 entity_type = Column(SQLEnum(JiraLinkEntityType), nullable=False)
     entity_type = Column(SQLEnum(JiraLinkEntityType), nullable=False)
+    # Assign entity_id = Column(UUID(as_uuid=True), nullable=False)
     entity_id = Column(UUID(as_uuid=True), nullable=False)
+    # Assign jira_issue_key = Column(String(50), nullable=False)
     jira_issue_key = Column(String(50), nullable=False)
+    # Assign jira_issue_id = Column(String(50))
     jira_issue_id = Column(String(50))
+    # Assign jira_project_key = Column(String(20))
     jira_project_key = Column(String(20))
+    # Assign jira_status = Column(String(100))
     jira_status = Column(String(100))
+    # Assign jira_priority = Column(String(50))
     jira_priority = Column(String(50))
+    # Assign jira_assignee = Column(String(255))
     jira_assignee = Column(String(255))
+    # Assign jira_story_points = Column(String(10))
     jira_story_points = Column(String(10))
+    # Assign sync_direction = Column(
     sync_direction = Column(
         SQLEnum(JiraSyncDirection), default=JiraSyncDirection.bidirectional
     )
+    # Assign last_synced_at = Column(DateTime)
     last_synced_at = Column(DateTime)
+    # Assign sync_metadata = Column(JSONB, default={})
     sync_metadata = Column(JSONB, default={})
+    # Assign created_by = Column(UUID(as_uuid=True), ForeignKey("users.id"))
     created_by = Column(UUID(as_uuid=True), ForeignKey("users.id"))
+    # Assign created_at = Column(DateTime(timezone=True), server_default=func.now())
     created_at = Column(DateTime(timezone=True), server_default=func.now())
+    # Assign updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate...
     updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now())
 
+    # Assign creator = relationship("User", foreign_keys=[created_by])
     creator = relationship("User", foreign_keys=[created_by])
 
+    # Assign __table_args__ = (
     __table_args__ = (
         Index("ix_jira_links_entity_id", "entity_id"),
         Index("ix_jira_links_issue_key", "jira_issue_key"),