M8-T16: add thermal meter cost APIs

app/schemas/meter_cost.py

@@ -0,0 +1,62 @@
+"""Schemas for the commodity-scoped thermal cost ledger."""
+
+from __future__ import annotations
+
+from datetime import datetime
+from typing import Literal
+
+from pydantic import BaseModel, Field
+
+
+class MeterCostPeriodSchema(BaseModel):
+    """One auditable thermal ledger row; all Decimal values are JSON strings."""
+
+    commodity: Literal["heating", "hot_water"]
+    period_start: datetime
+    period_end: datetime
+    meter_id: int | None
+    source_binding_id: int | None
+    contract_version_id: int | None
+    quantity: str
+    cost: str
+    currency: str
+    cost_breakdown: dict[str, str]
+    pricing_snapshot: dict[str, dict[str, str]]
+    quality: str
+    degraded: bool
+    degraded_reason: str | None
+
+
+class MeterCostsResponse(BaseModel):
+    items: list[MeterCostPeriodSchema]
+    total: int = Field(description="Total matching rows before pagination.")
+
+
+class ThermalFixedBreakdown(BaseModel):
+    """D11 annual-standing charges accrued per settled local day, as Decimal strings."""
+
+    heating_network: str
+    metering: str
+    delivery_set: str
+    hot_water_network: str
+    other: str
+
+
+class ThermalCostSummaryResponse(BaseModel):
+    currency: str
+    heating: str
+    hot_water_heating: str
+    hot_water: str
+    hot_water_tax: str
+    variable_subtotal: str
+    fixed_breakdown: ThermalFixedBreakdown
+    fixed_subtotal: str
+    all_in: str
+    period_count: int
+    degraded_count: int
+
+
+class MeterCostRecomputeResponse(BaseModel):
+    processed: int
+    normal: int
+    degraded: int