M5: Blazor dashboard (MudBlazor + ApexCharts)

- MudBlazor theme (dark default) + responsive drawer/appbar layout + nav.
- DashboardService read model: KPIs with period-over-period deltas, category breakdown,
  "what cost more/less" difference view, monthly trends.
- Pages: Overview (KPI cards + DeltaChip + donut + difference table), Trends (range-select
  bar chart), Meters (list + source status), Import (load reference dataset + CSV dry-run
  preview), Admin (energy types, tariffs). Charts isolated into components to avoid the
  ApexCharts/MudBlazor Color/Format name clashes.
- ReferenceDataImporter: one-click load of all four sheets as a starter dataset (meters,
  tank, tariff history, category memberships) — bundled sample CSVs copied to app output.
- End-to-end render test: import creates meters + consumption; overview/meters/trends/
  import/admin pages all return 200 with KPI cards rendered.

92 tests green (56 Core + 36 integration).

Deferred to polish: dedicated PV & oil/consumable panels, meter-detail page, full admin
CRUD, prev-year trend overlay.

Claude-Session: https://claude.ai/code/session_01WujdMtMJPbxDpDnMeK22rr

src/Infrastructure/DependencyInjection.cs

@@ -25,9 +25,11 @@ public static class DependencyInjection
         services.AddScoped<NormalizationService>();
         services.AddScoped<CsvImporter>();
         services.AddScoped<ImportService>();
+        services.AddScoped<ReferenceDataImporter>();
         services.AddScoped<IngestionService>();
         services.AddScoped<MqttMessageRouter>();
         services.AddScoped<Costing.CostService>();
+        services.AddScoped<Dashboard.DashboardService>();
 
         return services;
     }