feat(ai): add support for Ollama AI provider configuration

* Update README with Ollama integration details
* Add Ollama configuration to example YAML files
* Implement Ollama provider in AI factory
* Add tests for Ollama provider functionality
* Enhance config validation for Ollama settings

internal/config/config.go

@@ -62,6 +62,7 @@ type AIConfig struct {
 	Embeddings AIEmbeddingConfig  `yaml:"embeddings"`
 	Metadata   AIMetadataConfig   `yaml:"metadata"`
 	LiteLLM    LiteLLMConfig      `yaml:"litellm"`
+	Ollama     OllamaConfig       `yaml:"ollama"`
 	OpenRouter OpenRouterAIConfig `yaml:"openrouter"`
 }
 
@@ -84,6 +85,12 @@ type LiteLLMConfig struct {
 	MetadataModel   string            `yaml:"metadata_model"`
 }
 
+type OllamaConfig struct {
+	BaseURL        string            `yaml:"base_url"`
+	APIKey         string            `yaml:"api_key"`
+	RequestHeaders map[string]string `yaml:"request_headers"`
+}
+
 type OpenRouterAIConfig struct {
 	BaseURL      string            `yaml:"base_url"`
 	APIKey       string            `yaml:"api_key"`