feat(config): añade Settings con Pydantic Settings y .env loading

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

core/src/agentforge_core/config.py

@@ -0,0 +1,50 @@
+"""Configuración global del core. Se carga desde variables de entorno (.env)."""
+
+from __future__ import annotations
+
+from pathlib import Path
+from typing import Literal
+
+from pydantic import Field
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    """Settings tipadas. Pydantic falla en arranque si una requerida no está."""
+
+    model_config = SettingsConfigDict(
+        env_file=".env",
+        env_file_encoding="utf-8",
+        case_sensitive=False,
+        extra="ignore",
+    )
+
+    # LLM
+    llm_provider: Literal["mock", "azure", "openai"] = "mock"
+    llm_fallback_provider: Literal["mock", "azure", "openai", ""] = ""
+
+    # Azure OpenAI
+    azure_openai_endpoint: str = ""
+    azure_openai_api_key: str = ""
+    azure_openai_deployment: str = ""
+    azure_openai_api_version: str = "2024-08-01-preview"
+
+    # OpenAI
+    openai_api_key: str = ""
+    openai_model: str = "gpt-4o"
+
+    # Guardrails
+    guardrails_nemo_enabled: bool = False
+
+    # Observabilidad
+    log_level: Literal["DEBUG", "INFO", "WARNING", "ERROR"] = "INFO"
+
+    # Persistencia
+    data_dir: Path = Field(default=Path("./data"))
+    agents_dir: Path = Field(default=Path("./agents"))
+    policies_dir: Path = Field(default=Path("./policies"))
+
+
+def get_settings() -> Settings:
+    """Helper para inyección por dependencia en FastAPI."""
+    return Settings()