Add embeddings support and profile settings layer

[wesen]

Adds support for embeddings in Elasticsearch queries and improves configuration
handling:

Core Changes:

• Add !Embeddings tag support for generating embeddings in queries
• Add embeddings configuration layer with support for OpenAI and Ollama providers
• Add profile settings layer for persistent configuration
• Move documentation to pkg/doc for better organization

Embedding Features:

• Support for OpenAI and Ollama embedding providers
• Configurable via CLI flags, env vars, config files, or query-specific settings
• Default configurations for common use cases
• Comprehensive documentation for embeddings usage

Configuration Improvements:

• Add profile support for persistent settings
• Use XDG config directory for profile storage
• Improve layer merging behavior
• Add example queries demonstrating embeddings usage