v0.8.0 — replace moondream with gemma3:4b, add ollama tests

New:
- ollama test suite (4 tests: model registration, chat, embedding, vision)
- tests/.fixtures/cow.jpg for vision verification
- gemma3:4b as vision+chat model (replaces broken moondream)

Changed:
- ollama provider: moondream → gemma3:4b (general chat + vision)
- test_litellm.sh: conditionally checks ollama models when OLLAMA=1

Removed:
- moondream from pull list (broken, unmaintained GGUF)
- llama-swap config remnants from .env