expose: buy/sell_price_now follow the live dual-tariff slot

Subscribe the separate DSMR tariff topic (dsmr/meter-stats/electricity_tariff,
1=dal/off-peak, 2=normal/peak), keep the latest slot in memory, and make the
manual-contract buy/sell_price_now sensors show the matching tariff's price
(tariff 1 -> dal, 2/unknown -> normal). Tibber (single 15-min price) unchanged.
Billing is untouched (register-split already handles tariffs correctly).

- new config dsmr_tariff_topic; subscribe managed by apply_dsmr_subscription
  (restart-free on config save). In-memory tariff is lock-guarded.
- import_cost_total / export_revenue_total cumulative getters unchanged.

tests/test_energy_expose.py

@@ -1117,3 +1117,211 @@ def test_export_revenue_total_falls_back_to_sum_when_no_active_contract(energy_d
     assert value == pytest.approx(2.00, rel=1e-9), (
         f"Expected pure SUM=2.00 with no active contract, got {value!r}"
     )
+
+
+# ---------------------------------------------------------------------------
+# 15. Tariff-aware pricing: buy_price_now / sell_price_now honour _current_tariff
+# ---------------------------------------------------------------------------
+
+
+_DUAL_TARIFF_PRICING = {
+    "kind": "manual",
+    "buy_dal": "0.2500",
+    "buy_normal": "0.2700",
+    "sell_dal": "0.0900",
+    "sell_normal": "0.0950",
+    "energy_tax": "0.1234",
+    "ode": "0.0015",
+}
+
+
+@pytest.fixture()
+def reset_tariff(monkeypatch):
+    """Reset dsmr_ingest._current_tariff to None before/after each tariff test."""
+    from app.services import dsmr_ingest as _di
+
+    monkeypatch.setattr(_di, "_current_tariff", None)
+    yield
+
+
+def _insert_manual_period(energy_db) -> None:
+    """Insert a single non-degraded manual pricing period into energy_db."""
+    t0 = datetime(2026, 3, 1, 10, 0, tzinfo=timezone.utc)
+    with Session(energy_db) as session:
+        _make_period(
+            session,
+            period_start=t0,
+            import_cost=0.10,
+            export_revenue=0.05,
+            currency="EUR",
+            pricing=_DUAL_TARIFF_PRICING,
+            degraded=False,
+        )
+        session.commit()
+
+
+def test_buy_price_tariff_1_returns_dal(energy_db, reset_tariff) -> None:
+    """buy_price_now must return buy_dal when tariff=1 (off-peak)."""
+    from app.integrations.expose import build_catalog
+    from app.services.dsmr_ingest import set_current_tariff
+
+    _insert_manual_period(energy_db)
+    set_current_tariff(1)
+
+    with Session(energy_db) as session:
+        catalog = build_catalog(session)
+        buy_entry = next(e for e in catalog if e.entity.key == "energy.buy_price_now")
+        value = buy_entry.entity.value_getter(session)
+
+    assert value == pytest.approx(0.2500), f"Expected buy_dal=0.2500, got {value!r}"
+
+
+def test_buy_price_tariff_2_returns_normal(energy_db, reset_tariff) -> None:
+    """buy_price_now must return buy_normal when tariff=2 (peak)."""
+    from app.integrations.expose import build_catalog
+    from app.services.dsmr_ingest import set_current_tariff
+
+    _insert_manual_period(energy_db)
+    set_current_tariff(2)
+
+    with Session(energy_db) as session:
+        catalog = build_catalog(session)
+        buy_entry = next(e for e in catalog if e.entity.key == "energy.buy_price_now")
+        value = buy_entry.entity.value_getter(session)
+
+    assert value == pytest.approx(0.2700), f"Expected buy_normal=0.2700, got {value!r}"
+
+
+def test_buy_price_tariff_none_falls_back_to_normal(energy_db, reset_tariff) -> None:
+    """buy_price_now must return buy_normal when tariff is None (no DSMR tariff received yet)."""
+    from app.integrations.expose import build_catalog
+    from app.services.dsmr_ingest import set_current_tariff
+
+    _insert_manual_period(energy_db)
+    set_current_tariff(None)  # explicitly None (no tariff received)
+
+    with Session(energy_db) as session:
+        catalog = build_catalog(session)
+        buy_entry = next(e for e in catalog if e.entity.key == "energy.buy_price_now")
+        value = buy_entry.entity.value_getter(session)
+
+    assert value == pytest.approx(0.2700), f"Expected buy_normal=0.2700 fallback, got {value!r}"
+
+
+def test_sell_price_tariff_1_returns_dal(energy_db, reset_tariff) -> None:
+    """sell_price_now must return sell_dal when tariff=1 (off-peak)."""
+    from app.integrations.expose import build_catalog
+    from app.services.dsmr_ingest import set_current_tariff
+
+    _insert_manual_period(energy_db)
+    set_current_tariff(1)
+
+    with Session(energy_db) as session:
+        catalog = build_catalog(session)
+        sell_entry = next(e for e in catalog if e.entity.key == "energy.sell_price_now")
+        value = sell_entry.entity.value_getter(session)
+
+    assert value == pytest.approx(0.0900), f"Expected sell_dal=0.0900, got {value!r}"
+
+
+def test_sell_price_tariff_2_returns_normal(energy_db, reset_tariff) -> None:
+    """sell_price_now must return sell_normal when tariff=2 (peak)."""
+    from app.integrations.expose import build_catalog
+    from app.services.dsmr_ingest import set_current_tariff
+
+    _insert_manual_period(energy_db)
+    set_current_tariff(2)
+
+    with Session(energy_db) as session:
+        catalog = build_catalog(session)
+        sell_entry = next(e for e in catalog if e.entity.key == "energy.sell_price_now")
+        value = sell_entry.entity.value_getter(session)
+
+    assert value == pytest.approx(0.0950), f"Expected sell_normal=0.0950, got {value!r}"
+
+
+def test_sell_price_tariff_none_falls_back_to_normal(energy_db, reset_tariff) -> None:
+    """sell_price_now must return sell_normal when tariff is None."""
+    from app.integrations.expose import build_catalog
+    from app.services.dsmr_ingest import set_current_tariff
+
+    _insert_manual_period(energy_db)
+    set_current_tariff(None)
+
+    with Session(energy_db) as session:
+        catalog = build_catalog(session)
+        sell_entry = next(e for e in catalog if e.entity.key == "energy.sell_price_now")
+        value = sell_entry.entity.value_getter(session)
+
+    assert value == pytest.approx(0.0950), f"Expected sell_normal=0.0950 fallback, got {value!r}"
+
+
+def test_tibber_buy_price_not_affected_by_tariff(energy_db, reset_tariff) -> None:
+    """Tibber buy_price_now must NOT be affected by the DSMR tariff — always uses 'buy' key."""
+    from app.integrations.expose import build_catalog
+    from app.services.dsmr_ingest import set_current_tariff
+
+    t0 = datetime(2026, 4, 1, 9, 0, tzinfo=timezone.utc)
+    tibber_pricing = {
+        "kind": "tibber",
+        "buy": "0.3100",
+        "sell": "0.1500",
+        "energy_tax": "0.1234",
+        "sell_adjust": "0.0100",
+        "total": "0.3100",
+    }
+
+    with Session(energy_db) as session:
+        _make_period(
+            session,
+            period_start=t0,
+            pricing=tibber_pricing,
+            degraded=False,
+        )
+        session.commit()
+
+    # Tibber pricing must return the same value regardless of tariff.
+    for tariff_val in (1, 2, None):
+        set_current_tariff(tariff_val)
+        with Session(energy_db) as session:
+            catalog = build_catalog(session)
+            buy_entry = next(e for e in catalog if e.entity.key == "energy.buy_price_now")
+            value = buy_entry.entity.value_getter(session)
+        assert value == pytest.approx(0.3100), (
+            f"Tibber buy price must be 0.3100 regardless of tariff={tariff_val!r}, got {value!r}"
+        )
+
+
+def test_tibber_sell_price_not_affected_by_tariff(energy_db, reset_tariff) -> None:
+    """Tibber sell_price_now must NOT be affected by the DSMR tariff — always uses 'sell' key."""
+    from app.integrations.expose import build_catalog
+    from app.services.dsmr_ingest import set_current_tariff
+
+    t0 = datetime(2026, 4, 1, 9, 15, tzinfo=timezone.utc)
+    tibber_pricing = {
+        "kind": "tibber",
+        "buy": "0.3100",
+        "sell": "0.1500",
+        "energy_tax": "0.1234",
+        "sell_adjust": "0.0100",
+        "total": "0.3100",
+    }
+
+    with Session(energy_db) as session:
+        _make_period(
+            session,
+            period_start=t0,
+            pricing=tibber_pricing,
+            degraded=False,
+        )
+        session.commit()
+
+    for tariff_val in (1, 2, None):
+        set_current_tariff(tariff_val)
+        with Session(energy_db) as session:
+            catalog = build_catalog(session)
+            sell_entry = next(e for e in catalog if e.entity.key == "energy.sell_price_now")
+            value = sell_entry.entity.value_getter(session)
+        assert value == pytest.approx(0.1500), (
+            f"Tibber sell price must be 0.1500 regardless of tariff={tariff_val!r}, got {value!r}"
+        )