Ollama embedding support

[TerminalGravity]

Add Ollama as a local embedding provider for users who already have it running. No external API needed.

[TerminalGravity]

PR #81 implements this — adds Ollama as a local embedding provider with configurable base URL, model, and dimensions. Defaults to nomic-embed-text at 768 dims. Should be ready to merge once it gets a review.