### config.py

```python
import os
from functools import lru_cache
from typing import Optional

from pydantic import BaseSettings, Field


class Settings(BaseSettings):
    """Configuração centralizada da aplicação para.AI."""

    # Ambiente
    app_name: str = Field(default="para.AI", env="APP_NAME")
    app_env: str = Field(default="dev", env="APP_ENV")
    debug: bool = Field(default=True, env="DEBUG")
    log_level: str = Field(default="INFO", env="LOG_LEVEL")

    # Banco de dados
    database_url: str = Field(
        default="postgresql://para_ai:para_ai@db:5432/para_ai",
        env="DATABASE_URL",
    )
    db_pool_size: int = Field(default=20, env="DB_POOL_SIZE")
    db_max_overflow: int = Field(default=40, env="DB_MAX_OVERFLOW")

    # Arquivos
    files_base_path: str = Field(default="./data/files", env="FILES_BASE_PATH")

    # LLMs – chaves de API
    groq_api_key: Optional[str] = Field(default=None, env="GROQ_API_KEY")
    openai_api_key: Optional[str] = Field(default=None, env="OPENAI_API_KEY")
    anthropic_api_key: Optional[str] = Field(default=None, env="ANTHROPIC_API_KEY")

    # LLMs – limites e tuning
    llm_default_model_type: str = Field(
        default="balanced", env="LLM_DEFAULT_MODEL_TYPE"
    )
    llm_max_tokens: int = Field(default=2048, env="LLM_MAX_TOKENS")
    llm_temperature: float = Field(default=0.7, env="LLM_TEMPERATURE")

    class Config:
        env_file = ".env"
        env_file_encoding = "utf-8"
        case_sensitive = False


@lru_cache(maxsize=1)
def get_settings() -> Settings:
    """Retorna instância singleton de Settings."""
    return Settings()