feat: Docker, health check, schema migrations y webhook opt-in

- migrations/001_initial_schema.sql: DDL idempotente con CREATE TABLE/INDEX IF NOT EXISTS
- database.py: run_migrations() aplica .sql pendientes en orden; init_db() queda como alias
- health.py: servidor aiohttp en puerto 8080 — GET /health, GET /health/history, POST /webhook
  Watcher loop alerta al admin por Telegram si el poller no actualiza en N horas
- config.py: webhook_url, webhook_secret, health_port, health_alert_hours
- poller.py: on_poll_done callback (conecta con health.record_poll)
- main.py: arranca HealthServer, llama run_migrations, modo webhook opt-in via WEBHOOK_URL
- Dockerfile + docker-compose.yml + .dockerignore
- pyproject.toml: aiohttp>=3.9

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -14,6 +14,7 @@ dependencies = [
     "structlog>=24.4",
     "python-dotenv>=1.0",
     "aiosqlite>=0.20",
+    "aiohttp>=3.9",
 ]
 
 [dependency-groups]