feat: metabase_setup Python, fix list_databases, volumen Docker en init_metabase

Nueva función metabase_setup para setup inicial via API. Fix list_databases
que no extraía data del response wrapper. Pipeline init_metabase soporta
--mb-volumes para montar SQLite como volumen con fix de permisos automático.
Añadido .env a gitignore.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

python/functions/metabase/metabase_add_database.md

@@ -0,0 +1,44 @@
+---
+name: metabase_add_database
+kind: function
+lang: py
+domain: infra
+version: "1.0.0"
+purity: impure
+signature: "def metabase_add_database(client: MetabaseClient, name: str, engine: str, details: dict) -> dict"
+description: "Agrega una nueva database a Metabase via POST /api/database. Soporta cualquier engine (sqlite, postgres, mysql, etc.)."
+tags: [metabase, database, add, create, api, python]
+uses_functions: []
+uses_types: [MetabaseClient_go_infra]
+returns: []
+returns_optional: false
+error_type: "error_go_core"
+imports: [httpx]
+tested: false
+tests: []
+test_file_path: ""
+file_path: "python/functions/metabase/databases.py"
+---
+
+## Ejemplo
+
+```python
+# SQLite
+db = metabase_add_database(client, "Ops DB", "sqlite", {"db": "/data/operations.db"})
+print(db["id"])
+
+# Postgres
+db = metabase_add_database(client, "Prod PG", "postgres", {
+    "host": "localhost",
+    "port": 5432,
+    "dbname": "myapp",
+    "user": "reader",
+    "password": "secret",
+})
+```
+
+## Notas
+
+Requiere permisos de superusuario. El campo `details` depende del engine:
+para SQLite solo necesita `{"db": "/ruta/archivo.db"}`.
+Retorna la database creada con su `id` asignado por Metabase.