Refactor Unified API for stable MoE execution with Multi-Modal Routin…

[harshdesaii]

Description

Refactored the Unified API to fix MoE initialization and routing issues by correcting factory setup, expert creation, and router integration. Added deterministic multi-modal routing with equal weight distribution across active experts, standardized response formats, and improved validation.

Fixes # (issue)

• Fixed incorrect MoE factory usage that caused Unknown MoE model type errors.
• Fixed router instantiation bug caused by using abstract ExpertRouter.
• Updated modality router to distribute weights evenly across matched experts.
• Added real experts in the API:

  text_expert
  Default LLM provider via factory

  image_expert
  OpenAI Vision if API key exists
  otherwise Ollama Vision fallback

  audio_expert
  OpenAI Whisper if API key exists

• Fixed request packing to support multiple inputs per modality.
• Standardized API response format.