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

tests/Integration.Tests/MeterVaultAppFactory.cs

@@ -0,0 +1,18 @@
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Mvc.Testing;
+
+namespace MeterVault.Integration.Tests;
+
+/// <summary>
+/// Boots the real ASP.NET Core app in-memory against the shared Timescale container.
+/// Migrations are already applied by <see cref="TimescaleFixture"/>, so startup migration is off.
+/// </summary>
+public sealed class MeterVaultAppFactory(string connectionString) : WebApplicationFactory<Program>
+{
+    protected override void ConfigureWebHost(IWebHostBuilder builder)
+    {
+        builder.UseEnvironment("Testing");
+        builder.UseSetting("ConnectionStrings:Default", connectionString);
+        builder.UseSetting("MeterVault:RunMigrationsAtStartup", "false");
+    }
+}