chore(backend): standardize multiline formatting across modules

Reformatted multiline function calls, object definitions, and queries for improved code readability and consistency. Adjusted imports and constraints where necessary.

backend/app/schemas/events.py

@@ -205,9 +205,7 @@ class SprintCompletedPayload(BaseModel):
     sprint_id: UUID = Field(..., description="Sprint ID")
     sprint_name: str = Field(..., description="Sprint name")
     completed_issues: int = Field(default=0, description="Number of completed issues")
-    incomplete_issues: int = Field(
-        default=0, description="Number of incomplete issues"
-    )
+    incomplete_issues: int = Field(default=0, description="Number of incomplete issues")
 
 
 class ApprovalRequestedPayload(BaseModel):

backend/app/schemas/syndarix/issue.py

@@ -99,9 +99,7 @@ class IssueAssign(BaseModel):
     def validate_assignment(self) -> "IssueAssign":
         """Ensure only one type of assignee is set."""
         if self.assigned_agent_id and self.human_assignee:
-            raise ValueError(
-                "Cannot assign to both an agent and a human. Choose one."
-            )
+            raise ValueError("Cannot assign to both an agent and a human. Choose one.")
         return self