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.

openapi/openapi.json

@@ -4727,17 +4727,27 @@
           "metered_import": {
             "type": "number",
             "title": "Metered Import",
-            "description": "Σ import_cost for non-degraded periods."
+            "description": "Σ import_cost for non-degraded periods (money, in `currency`)."
           },
           "metered_export": {
             "type": "number",
             "title": "Metered Export",
-            "description": "Σ export_revenue for non-degraded periods."
+            "description": "Σ export_revenue for non-degraded periods (money, in `currency`)."
           },
           "metered_net": {
             "type": "number",
             "title": "Metered Net",
-            "description": "Σ net_cost for non-degraded periods."
+            "description": "Σ net_cost for non-degraded periods (money, in `currency`)."
+          },
+          "metered_import_kwh": {
+            "type": "number",
+            "title": "Metered Import Kwh",
+            "description": "Σ (d1_kwh + d2_kwh) for non-degraded periods (energy imported, kWh)."
+          },
+          "metered_export_kwh": {
+            "type": "number",
+            "title": "Metered Export Kwh",
+            "description": "Σ (r1_kwh + r2_kwh) for non-degraded periods (energy exported, kWh)."
           },
           "fixed_costs": {
             "type": "number",
@@ -4776,6 +4786,8 @@
           "metered_import",
           "metered_export",
           "metered_net",
+          "metered_import_kwh",
+          "metered_export_kwh",
           "fixed_costs",
           "credits",
           "total_payable",
@@ -4784,7 +4796,7 @@
           "days"
         ],
         "title": "SummaryResponse",
-        "description": "Response for GET /api/energy/costs/summary.\n\nAll monetary values are in ``currency``.\n\n``total_payable = metered_net + fixed_costs − credits``"
+        "description": "Response for GET /api/energy/costs/summary.\n\nMonetary values are in ``currency``; the ``*_kwh`` fields are energy totals\nin kWh.  ``metered_import``/``metered_export`` are **money**, not energy —\nonly the ``_kwh``-suffixed fields carry kWh.\n\n``total_payable = metered_net + fixed_costs − credits``"
       },
       "TibberTestPriceSchema": {
         "properties": {

openapi/openapi.yaml

@@ -3659,15 +3659,25 @@ components:
         metered_import:
           type: number
           title: Metered Import
-          description: Σ import_cost for non-degraded periods.
+          description: Σ import_cost for non-degraded periods (money, in `currency`).
         metered_export:
           type: number
           title: Metered Export
-          description: Σ export_revenue for non-degraded periods.
+          description: Σ export_revenue for non-degraded periods (money, in `currency`).
         metered_net:
           type: number
           title: Metered Net
-          description: Σ net_cost for non-degraded periods.
+          description: Σ net_cost for non-degraded periods (money, in `currency`).
+        metered_import_kwh:
+          type: number
+          title: Metered Import Kwh
+          description: Σ (d1_kwh + d2_kwh) for non-degraded periods (energy imported,
+            kWh).
+        metered_export_kwh:
+          type: number
+          title: Metered Export Kwh
+          description: Σ (r1_kwh + r2_kwh) for non-degraded periods (energy exported,
+            kWh).
         fixed_costs:
           type: number
           title: Fixed Costs
@@ -3699,6 +3709,8 @@ components:
       - metered_import
       - metered_export
       - metered_net
+      - metered_import_kwh
+      - metered_export_kwh
       - fixed_costs
       - credits
       - total_payable
@@ -3709,7 +3721,11 @@ components:
       description: '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``'