Add Ollama local-model provider for zero-cost development

[SinghCod3r]

Add an optional Ollama provider so SkillFoundry can run with locally hosted models without requiring a paid cloud API.

Requirements:

• No API key required.
• Configurable model name.
• Configurable localhost base URL.
• Clear error when Ollama is unavailable.
• Use the existing provider abstraction.
• Add provider tests.
• Preserve existing providers.

This would make local development much easier for contributors.