feat(providers): add Ollama provider support

- Implement OllamaProvider with OpenAI-compatible API integration
- Add Ollama to provider initialization in server.go
- Update config.go to handle Ollama (no API key required)
- Configure .env with Ollama server at 172.20.1.222:11434
- Support models: glm-4.7-flash:latest, qwen3-coder:30b, gemma4:26b

internal/config/config.go

@@ -195,6 +195,9 @@ func (c *Config) GetAPIKey(provider string) (string, error) {
 		envVar = c.Providers.Moonshot.APIKeyEnv
 	case "grok":
 		envVar = c.Providers.Grok.APIKeyEnv
+	case "ollama":
+		// Ollama doesn't require an API key
+		return "", nil
 	default:
 		return "", fmt.Errorf("unknown provider: %s", provider)
 	}