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>

.env.example

@@ -1,15 +1,57 @@
 # Core Code API Configuration
+# Copy to .env and fill in real values
 
-# Application settings
+# =============================================================================
+# Application
+# =============================================================================
 APP_NAME="Core Code API"
 DEBUG=false
+LOG_LEVEL=INFO
 
-# Server settings
+# =============================================================================
+# Server
+# =============================================================================
 HOST=0.0.0.0
 PORT=8083
 
-# CORS settings (default allows all origins for internal use)
+# CORS (default allows all origins for internal use)
 # CORS_ORIGINS=["http://192.168.86.149:82"]
 
-# Logging
-LOG_LEVEL=INFO
+# =============================================================================
+# Infrastructure Services
+# =============================================================================
+
+# Portainer API (required for container/stack management)
+PORTAINER_URL=http://portainer:9000
+PORTAINER_API_KEY=ptr_your-api-key-here
+
+# Nginx Proxy Manager API
+NPM_URL=http://npm:81
+NPM_EMAIL=admin@example.com
+NPM_PASSWORD=your-npm-password
+
+# =============================================================================
+# Home Automation
+# =============================================================================
+
+# Home Assistant API
+HOMEASSISTANT_URL=http://homeassistant:8123
+HOMEASSISTANT_TOKEN=your-long-lived-access-token
+
+# =============================================================================
+# AI Services
+# =============================================================================
+
+# Ollama API
+OLLAMA_BASE_URL=http://ollama:11434
+
+# SearXNG (self-hosted search)
+SEARXNG_URL=http://searxng:8080
+
+# =============================================================================
+# Vector Database
+# =============================================================================
+
+# Qdrant
+QDRANT_HOST=qdrant
+QDRANT_PORT=6333