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.

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

backend/app/schemas/jira_schema.py

@@ -1,46 +1,91 @@
 """Pydantic schemas for Jira integration endpoints."""
 
+# Import datetime from datetime
 from datetime import datetime
+
+# Import Optional from typing
 from typing import Optional
+
+# Import UUID from uuid
 from uuid import UUID
 
+# Import BaseModel, Field from pydantic
 from pydantic import BaseModel, Field
 
+# Import JiraLinkEntityType, JiraSyncDirection from app.models.jira_link
 from app.models.jira_link import JiraLinkEntityType, JiraSyncDirection
 
 
+# Define class JiraLinkCreate
 class JiraLinkCreate(BaseModel):
+    """Payload for linking an Aegis entity to an existing Jira issue."""
+
+    # entity_type: JiraLinkEntityType
     entity_type: JiraLinkEntityType
+    # entity_id: UUID
     entity_id: UUID
+    # Assign jira_issue_key = Field(..., pattern=r"^[A-Z][A-Z0-9]+-\d+$")
     jira_issue_key: str = Field(..., pattern=r"^[A-Z][A-Z0-9]+-\d+$")
+    # Assign sync_direction = JiraSyncDirection.bidirectional
     sync_direction: JiraSyncDirection = JiraSyncDirection.bidirectional
 
 
+# Define class JiraLinkOut
 class JiraLinkOut(BaseModel):
+    """Full representation of a Jira link returned by the API."""
+
+    # id: UUID
     id: UUID
+    # entity_type: JiraLinkEntityType
     entity_type: JiraLinkEntityType
+    # entity_id: UUID
     entity_id: UUID
+    # jira_issue_key: str
     jira_issue_key: str
+    # Assign jira_issue_id = None
     jira_issue_id: Optional[str] = None
+    # Assign jira_project_key = None
     jira_project_key: Optional[str] = None
+    # Assign jira_status = None
     jira_status: Optional[str] = None
+    # Assign jira_priority = None
     jira_priority: Optional[str] = None
+    # Assign jira_assignee = None
     jira_assignee: Optional[str] = None
+    # Assign jira_story_points = None
     jira_story_points: Optional[str] = None
+    # Assign last_synced_at = None
     last_synced_at: Optional[datetime] = None
+    # created_at: datetime
     created_at: datetime
 
+    # Define class Config
     class Config:
+        """ORM mode configuration for SQLAlchemy model mapping."""
+
+        # Assign from_attributes = True
         from_attributes = True
 
 
+# Define class JiraIssueSearch
 class JiraIssueSearch(BaseModel):
+    """Payload for searching Jira issues by free-text query."""
+
+    # query: str
     query: str
 
 
+# Define class JiraIssueResult
 class JiraIssueResult(BaseModel):
+    """Lightweight Jira issue representation returned by search results."""
+
+    # issue_key: str
     issue_key: str
+    # summary: str
     summary: str
+    # status: str
     status: str
+    # Assign assignee = None
     assignee: Optional[str] = None
+    # Assign priority = None
     priority: Optional[str] = None