M8-T01: add meter source identity schema

app/models/energy.py

@@ -13,12 +13,12 @@ from __future__ import annotations
 
 import uuid as _uuid
 from datetime import datetime
-
 from sqlalchemy import Boolean, DateTime, Float, ForeignKey, Integer, String
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 from sqlalchemy.types import JSON
 
 from app.db import Base
+from app.models.meter_source import MeterSourceBinding
 
 
 def _uuid4_str() -> str:
@@ -85,6 +85,10 @@ class Meter(Base):
         back_populates="meter", cascade="save-update, merge"
     )
 
+    source_bindings: Mapped[list["MeterSourceBinding"]] = relationship(
+        back_populates="meter", cascade="save-update, merge"
+    )
+
 
 class DsmrReading(Base):
     """One down-sampled DSMR telegram stored as a full JSON blob.
@@ -292,6 +296,12 @@ class EnergyCostPeriod(Base):
         ForeignKey("meter.id", ondelete="RESTRICT"), nullable=True
     )
 
+    # Nullable while M8 adopts historical DSMR rows.  Future normal periods
+    # will point at the binding that supplied both cumulative endpoints.
+    source_binding_id: Mapped[int | None] = mapped_column(
+        ForeignKey("meter_source_binding.id", ondelete="RESTRICT"), nullable=True
+    )
+
     # True when the period was computed with incomplete data (missing readings or
     # missing price); serves as a flag for later recomputation.
     degraded: Mapped[bool] = mapped_column(Boolean, nullable=False, default=False)
@@ -307,6 +317,10 @@ class EnergyCostPeriod(Base):
     # Relationship back to the meter epoch.
     meter: Mapped["Meter | None"] = relationship(back_populates="cost_periods")
 
+    source_binding: Mapped["MeterSourceBinding | None"] = relationship(
+        back_populates="cost_periods"
+    )
+
 
 # Index on recorded_at for efficient time-range queries on DSMR readings.
 # (The ORM-level index=True on recorded_at already creates ix_dsmr_reading_recorded_at;