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>

migrations/001_initial_schema.sql

@@ -0,0 +1,42 @@
+-- 001_initial_schema.sql — Schema base de Pedrito Hechakuaa
+-- Idempotente: usa CREATE TABLE/INDEX IF NOT EXISTS
+
+CREATE TABLE IF NOT EXISTS schema_migrations (
+    version    TEXT PRIMARY KEY,
+    applied_at TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS invite_codes (
+    codigo     TEXT PRIMARY KEY,
+    creado_at  TEXT NOT NULL,
+    usado      INTEGER DEFAULT 0,
+    usado_por  INTEGER,
+    usado_at   TEXT
+);
+
+CREATE TABLE IF NOT EXISTS tenants (
+    chat_id                 INTEGER PRIMARY KEY,
+    nombre_preferido        TEXT,
+    tono                    TEXT    DEFAULT 'cotidiano',
+    timezone                TEXT    DEFAULT 'America/Asuncion',
+    credentials_enc         TEXT,
+    estado                  TEXT    DEFAULT 'pendiente',
+    consentimiento_aceptado INTEGER DEFAULT 0,
+    created_at              TEXT,
+    last_active             TEXT
+);
+
+CREATE TABLE IF NOT EXISTS audit_log (
+    id              INTEGER PRIMARY KEY AUTOINCREMENT,
+    timestamp       TEXT    NOT NULL,
+    timestamp_local TEXT,
+    chat_id         INTEGER,
+    evento          TEXT    NOT NULL,
+    detalle         TEXT,
+    resultado       TEXT,
+    duracion_ms     INTEGER
+);
+
+CREATE INDEX IF NOT EXISTS idx_audit_chat_id   ON audit_log(chat_id);
+CREATE INDEX IF NOT EXISTS idx_audit_timestamp ON audit_log(timestamp);
+CREATE INDEX IF NOT EXISTS idx_audit_evento    ON audit_log(evento);