refactor: simplify configuration to use only environment variables

- Remove credentials.py import, use pydantic-settings .env support
- Remove unused search API keys (Brave, Google)
- Update default search provider to SearXNG
- Add extra="ignore" to allow flexible env var usage
- Update .env.example with organized sections

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/config.py

@@ -1,5 +1,8 @@
 """
 Global configuration for Core Code API
+
+All configuration is loaded from environment variables or .env file.
+See .env.example for available settings.
 """
 import tomllib
 from pathlib import Path
@@ -20,29 +23,6 @@ def _get_version_from_pyproject() -> str:
 
 __version__ = _get_version_from_pyproject()
 
-# Import infrastructure credentials from gitignored module
-try:
-    from src.credentials import (
-        PORTAINER_URL, PORTAINER_API_KEY,
-        NPM_URL, NPM_EMAIL, NPM_PASSWORD,
-        BRAVE_SEARCH_API_KEY,
-        GOOGLE_SEARCH_API_KEY, GOOGLE_SEARCH_ENGINE_ID,
-        HOMEASSISTANT_URL, HOMEASSISTANT_TOKEN
-    )
-except ImportError:
-    # Fallback to empty strings if credentials.py doesn't exist
-    # (e.g., fresh clone before credentials setup)
-    PORTAINER_URL = "http://localhost:8001"
-    PORTAINER_API_KEY = ""
-    NPM_URL = "http://localhost:81"
-    NPM_EMAIL = ""
-    NPM_PASSWORD = ""
-    BRAVE_SEARCH_API_KEY = ""
-    GOOGLE_SEARCH_API_KEY = ""
-    GOOGLE_SEARCH_ENGINE_ID = ""
-    HOMEASSISTANT_URL = "http://localhost:8123"
-    HOMEASSISTANT_TOKEN = ""
-
 
 class Settings(BaseSettings):
     """Global application settings"""
@@ -109,25 +89,21 @@ class Settings(BaseSettings):
     embedding_batch_size: int = 32
 
     # Search Configuration
-    search_provider: str = "google"  # Options: google, brave, searxng, duckduckgo
-    searxng_url: str = "http://searxng:8080"  # For future self-hosted SearxNG
+    search_provider: str = "searxng"
+    searxng_url: str = "http://searxng:8080"
 
-    # Search API Keys (from credentials.py)
-    brave_search_api_key: str = BRAVE_SEARCH_API_KEY  # https://brave.com/search/api/
-    google_search_api_key: str = GOOGLE_SEARCH_API_KEY  # https://console.cloud.google.com/
-    google_search_engine_id: str = GOOGLE_SEARCH_ENGINE_ID  # Custom Search Engine ID
+    # Infrastructure Management (Portainer)
+    portainer_url: str = "http://portainer:9000"
+    portainer_api_key: str = ""
 
-    # Infrastructure Management (from credentials.py)
-    portainer_url: str = PORTAINER_URL
-    portainer_api_key: str = PORTAINER_API_KEY
-
-    npm_url: str = NPM_URL
-    npm_email: str = NPM_EMAIL
-    npm_password: str = NPM_PASSWORD
+    # Infrastructure Management (Nginx Proxy Manager)
+    npm_url: str = "http://npm:81"
+    npm_email: str = ""
+    npm_password: str = ""
 
     # Home Assistant Configuration
-    homeassistant_url: str = HOMEASSISTANT_URL
-    homeassistant_token: str = HOMEASSISTANT_TOKEN
+    homeassistant_url: str = "http://homeassistant:8123"
+    homeassistant_token: str = ""
     homeassistant_timeout: int = 30
 
     # Core-AI Service (AI performance metrics)
@@ -163,6 +139,7 @@ class Settings(BaseSettings):
     class Config:
         env_file = ".env"
         case_sensitive = False
+        extra = "ignore"  # Ignore extra env vars not defined in Settings
 
 
 @lru_cache()