feat: support use ollama as embedding provider(#138)

[dishuostec]

Now we can use Ollama as a embedding provider as blow. (fix #138)

enable_event_embedding: true
embedding_provider: "ollama"
embedding_api_key: "ollama"
embedding_base_url: "http://127.0.0.1:11434/" # WITHOUT "v1" at the end
embedding_dim: 2560
embedding_model: "qwen3-embedding:4b-q4_K_M"

[gusye1234]

LGTM!

Can you also add example config.yaml for ollama embedding?

• https://github.com/memodb-io/memobase/tree/main/src/server/api/example_config
• Also update readme for ollama embedding example config path:

  memobase/src/server/readme.md

  Line 39 in 936f453

  - [`jina_embedding`](./api/example_config/jina_embedding) uses Jina exmbedding for event search.

[dishuostec]

It's done.