FUE-T04: add Meter.uuid (stable HA identity anchor) + backfill migration

tests/test_energy_models.py

@@ -798,7 +798,7 @@ def test_meter_columns(energy_db):
     inspector = inspect(energy_db)
     columns = {col["name"]: col for col in inspector.get_columns("meter")}
 
-    non_nullable = {"id", "label", "commodity", "started_at", "reason", "created_at"}
+    non_nullable = {"id", "uuid", "label", "commodity", "started_at", "reason", "created_at"}
     nullable = {"ended_at", "note"}
 
     for col_name in non_nullable:
@@ -810,11 +810,20 @@ def test_meter_columns(energy_db):
         assert columns[col_name]["nullable"], f"{col_name} should be nullable"
 
 
+def test_meter_uuid_unique_constraint(energy_db):
+    """meter.uuid must have a unique constraint."""
+    inspector = inspect(energy_db)
+    unique_constraints = inspector.get_unique_constraints("meter")
+    unique_cols = [col for uc in unique_constraints for col in uc["column_names"]]
+    assert "uuid" in unique_cols, "meter.uuid must have a unique constraint"
+
+
 def test_meter_orm_metadata():
     """Meter must be registered in Base.metadata with correct field types."""
     assert "meter" in Base.metadata.tables, "meter not in Base.metadata"
     table = Base.metadata.tables["meter"]
     assert "id" in table.columns
+    assert "uuid" in table.columns
     assert "label" in table.columns
     assert "commodity" in table.columns
     assert "started_at" in table.columns
@@ -824,6 +833,14 @@ def test_meter_orm_metadata():
     assert "created_at" in table.columns
 
 
+def test_meter_uuid_unique_in_metadata():
+    """Meter.uuid must be declared unique and not nullable in ORM metadata."""
+    table = Base.metadata.tables["meter"]
+    col = table.columns["uuid"]
+    assert col.unique, "Meter.uuid must be declared unique in ORM metadata"
+    assert not col.nullable, "Meter.uuid must be NOT NULL in ORM metadata"
+
+
 def test_meter_insert_and_retrieve(energy_db):
     """A Meter row can be inserted and retrieved with all fields intact."""
     now = datetime.now(tz=timezone.utc)