fix(energy): report real kWh in the cost Summary instead of mislabelled money

The Summary cards labelled `metered_import` / `metered_export` as "(kWh)", but
both fields are monetary totals (Σ import_cost / Σ export_revenue).  Today's
page therefore showed "Import 1.339 kWh" when the meter had actually imported
4.188 kWh — the 1.339 was EUR.  Cross-checked against the DSMR cumulative
registers and Home Assistant: our energy figures were correct all along, only
the label was wrong.

summarize() now also aggregates the metered energy, reusing the already-fetched
non-degraded rows so no extra query is issued:

  metered_import_kwh = Σ (d1_kwh + d2_kwh)
  metered_export_kwh = Σ (r1_kwh + r2_kwh)

The Import/Export cards show kWh as the headline figure and keep the monetary
equivalent as a sub-line, so the split between energy cost and standing
charges/credits behind total_payable stays visible.

The `_kwh` suffix is now the only thing separating energy from money in this
payload, so the docstrings on both summarize() and SummaryResponse call that
out explicitly.

app/integrations/expose.py reads only the money keys, so the HA outbound
sensors are unaffected by the additive fields.

app/schemas/energy.py

@@ -121,15 +121,29 @@ class CostsResponse(BaseModel):
 class SummaryResponse(BaseModel):
     """Response for GET /api/energy/costs/summary.
 
-    All monetary values are in ``currency``.
+    Monetary values are in ``currency``; the ``*_kwh`` fields are energy totals
+    in kWh.  ``metered_import``/``metered_export`` are **money**, not energy —
+    only the ``_kwh``-suffixed fields carry kWh.
 
     ``total_payable = metered_net + fixed_costs − credits``
     """
 
     currency: str
-    metered_import: float = Field(description="Σ import_cost for non-degraded periods.")
-    metered_export: float = Field(description="Σ export_revenue for non-degraded periods.")
-    metered_net: float = Field(description="Σ net_cost for non-degraded periods.")
+    metered_import: float = Field(
+        description="Σ import_cost for non-degraded periods (money, in `currency`)."
+    )
+    metered_export: float = Field(
+        description="Σ export_revenue for non-degraded periods (money, in `currency`)."
+    )
+    metered_net: float = Field(
+        description="Σ net_cost for non-degraded periods (money, in `currency`)."
+    )
+    metered_import_kwh: float = Field(
+        description="Σ (d1_kwh + d2_kwh) for non-degraded periods (energy imported, kWh)."
+    )
+    metered_export_kwh: float = Field(
+        description="Σ (r1_kwh + r2_kwh) for non-degraded periods (energy exported, kWh)."
+    )
     fixed_costs: float = Field(
         description="Standing charges (network_fee + management_fee) apportioned over the interval."
     )

app/services/energy_cost.py

@@ -18,6 +18,12 @@ M6 design document, extended in M7-T03 to be meter-aware:
   ÷ 30 per day) and subtracts the energy-tax credit (heffingskorting,
   apportioned at EUR/year ÷ 365 per day).
 
+  The summary reports **both** money and energy: ``metered_import`` /
+  ``metered_export`` are monetary totals (Σ import_cost / Σ export_revenue),
+  while ``metered_import_kwh`` / ``metered_export_kwh`` are the corresponding
+  metered energy totals in kWh.  The ``_kwh`` suffix is the only thing that
+  distinguishes them — always check it before labelling a value in a UI.
+
 Design notes
 ------------
 - **Decimal arithmetic throughout**: all monetary computations use
@@ -731,16 +737,18 @@ def summarize(session: Session, start: datetime, end: datetime) -> dict[str, Any
     -------
     dict with keys:
 
-        currency          str    ISO 4217 currency (from contract, or "EUR" fallback)
-        metered_import    float  Σ import_cost from non-degraded periods
-        metered_export    float  Σ export_revenue from non-degraded periods
-        metered_net       float  Σ net_cost from non-degraded periods
-        fixed_costs       float  standing charges for elapsed whole local days
-        credits           float  energy-tax credit for elapsed whole local days
-        total_payable     float  metered_net + fixed_costs − credits
-        period_count      int    number of non-degraded periods in range
-        degraded_count    int    number of degraded periods in range
-        days              float  interval length in days (total_seconds / 86400)
+        currency            str    ISO 4217 currency (from contract, or "EUR" fallback)
+        metered_import      float  Σ import_cost from non-degraded periods (money)
+        metered_export      float  Σ export_revenue from non-degraded periods (money)
+        metered_net         float  Σ net_cost from non-degraded periods (money)
+        metered_import_kwh  float  Σ (d1_kwh + d2_kwh) from non-degraded periods (energy)
+        metered_export_kwh  float  Σ (r1_kwh + r2_kwh) from non-degraded periods (energy)
+        fixed_costs         float  standing charges for elapsed whole local days
+        credits             float  energy-tax credit for elapsed whole local days
+        total_payable       float  metered_net + fixed_costs − credits
+        period_count        int    number of non-degraded periods in range
+        degraded_count      int    number of degraded periods in range
+        days                float  interval length in days (total_seconds / 86400)
     """
     from datetime import timedelta as _td, date as _date
 
@@ -763,6 +771,15 @@ def summarize(session: Session, start: datetime, end: datetime) -> dict[str, Any
     sum_export = sum((_to_decimal(r.export_revenue) for r in good_rows), Decimal("0"))
     sum_net = sum((_to_decimal(r.net_cost) for r in good_rows), Decimal("0"))
 
+    # Σ metered energy (kWh), summed across both tariff registers.  Reuses the
+    # already-fetched ``good_rows`` so no extra query is issued.
+    sum_import_kwh = sum(
+        (_to_decimal(r.d1_kwh) + _to_decimal(r.d2_kwh) for r in good_rows), Decimal("0")
+    )
+    sum_export_kwh = sum(
+        (_to_decimal(r.r1_kwh) + _to_decimal(r.r2_kwh) for r in good_rows), Decimal("0")
+    )
+
     # --- Interval length in days (window, not elapsed — kept for API compat) ---
     total_seconds = (end_utc - start_utc).total_seconds()
     days = _to_decimal(str(total_seconds)) / _to_decimal("86400")
@@ -885,6 +902,8 @@ def summarize(session: Session, start: datetime, end: datetime) -> dict[str, Any
         "metered_import": float(sum_import),
         "metered_export": float(sum_export),
         "metered_net": float(sum_net),
+        "metered_import_kwh": float(sum_import_kwh),
+        "metered_export_kwh": float(sum_export_kwh),
         "fixed_costs": float(fixed_dec),
         "credits": float(credits_dec),
         "total_payable": float(total_payable),