Added LM Studio Provider integration

[Sohailm25]

Summary

• add a local flyllm override with an LmStudio provider (model discovery via /v1/models, new
  instance implementation, unit tests)
• extend API config to persist custom endpoints, include LM Studio defaults, and expose generic set/
  get endpoint commands
• update the LLM manager to route LM Studio through flyllm using the custom endpoint
• refresh Settings → LLMs to support endpoint-based providers (Ollama + LM Studio), including
  validation and model refresh