refactor: update module docstrings for clarity and consistency

backend/app/schemas/metrics.py

@@ -1,17 +1,23 @@
+"""Dashboard metrics schemas for KPI and time-series API responses."""
+
 from __future__ import annotations
 
-from datetime import datetime
+from datetime import datetime  # noqa: TCH003
 from typing import Literal
 
 from sqlmodel import SQLModel
 
 
 class DashboardSeriesPoint(SQLModel):
+    """Single numeric time-series point."""
+
     period: datetime
     value: float
 
 
 class DashboardWipPoint(SQLModel):
+    """Work-in-progress point split by task status buckets."""
+
     period: datetime
     inbox: int
     in_progress: int
@@ -19,28 +25,38 @@ class DashboardWipPoint(SQLModel):
 
 
 class DashboardRangeSeries(SQLModel):
+    """Series payload for a single range/bucket combination."""
+
     range: Literal["24h", "7d"]
     bucket: Literal["hour", "day"]
     points: list[DashboardSeriesPoint]
 
 
 class DashboardWipRangeSeries(SQLModel):
+    """WIP series payload for a single range/bucket combination."""
+
     range: Literal["24h", "7d"]
     bucket: Literal["hour", "day"]
     points: list[DashboardWipPoint]
 
 
 class DashboardSeriesSet(SQLModel):
+    """Primary vs comparison pair for generic series metrics."""
+
     primary: DashboardRangeSeries
     comparison: DashboardRangeSeries
 
 
 class DashboardWipSeriesSet(SQLModel):
+    """Primary vs comparison pair for WIP status series metrics."""
+
     primary: DashboardWipRangeSeries
     comparison: DashboardWipRangeSeries
 
 
 class DashboardKpis(SQLModel):
+    """Topline dashboard KPI summary values."""
+
     active_agents: int
     tasks_in_progress: int
     error_rate_pct: float
@@ -48,6 +64,8 @@ class DashboardKpis(SQLModel):
 
 
 class DashboardMetrics(SQLModel):
+    """Complete dashboard metrics response payload."""
+
     range: Literal["24h", "7d"]
     generated_at: datetime
     kpis: DashboardKpis