feat: add centralized config layer

core/config.py

@@ -0,0 +1,20 @@
+from functools import lru_cache
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    APP_NAME: str = "Eroha AI Core"
+    DEBUG: bool = False
+
+    OPENAI_API_KEY: str = ""
+    MODEL_NAME: str = "gpt-4o-mini"
+
+    RATE_LIMIT: int = 20
+    TIMEOUT_SECONDS: int = 60
+
+    model_config = SettingsConfigDict(env_file=".env", extra="ignore")
+
+
+@lru_cache
+def get_settings() -> Settings:
+    return Settings()