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

.dockerignore

@@ -0,0 +1,13 @@
+**/bin/
+**/obj/
+**/.vs/
+**/.idea/
+.git/
+.github/
+docs/
+sampledata/
+tests/
+**/*.user
+**/appsettings.*.Local.json
+.env
+.env.*