M0: scaffold solution, EF+Timescale schema, /healthz

Five-project Clean Architecture solution (Core/Infrastructure/App + Core.Tests/
Integration.Tests) on .NET 10 with central package management, snake_case EF mapping,
and shared build/style config.

- Full domain entity set + EF DbContext for the SDD §5.3 schema (singular table names).
- InitialSchema migration (relational) + TimescaleHypertables migration (raw SQL:
  create_hypertable + compression on reading, hypertable on consumption).
- App wiring: Serilog (actually wired, unlike MQTTower), DbContext, migrate-on-startup,
  /healthz. Serves plain HTTP behind a reverse proxy (no HTTPS redirect).
- deploy/Dockerfile (2-stage, ICU-capable) + docker-compose (app + timescaledb).
- Integration.Tests: shared TimescaleFixture (Testcontainers) — migrations, hypertables,
  compression policy, and /healthz all verified green (4/4).

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

src/Infrastructure/DependencyInjection.cs

@@ -0,0 +1,22 @@
+using MeterVault.Infrastructure.Persistence;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace MeterVault.Infrastructure;
+
+/// <summary>Composition root for the infrastructure layer (persistence, ingestion, import).</summary>
+public static class DependencyInjection
+{
+    public static IServiceCollection AddMeterVaultInfrastructure(
+        this IServiceCollection services,
+        string connectionString)
+    {
+        services.AddDbContext<MeterVaultDbContext>(options =>
+            options
+                .UseNpgsql(connectionString, npgsql =>
+                    npgsql.MigrationsAssembly(typeof(MeterVaultDbContext).Assembly.FullName))
+                .UseSnakeCaseNamingConvention());
+
+        return services;
+    }
+}