refactor(domain): standardize metadata field naming to meta_data across all models

- Rename metadata fields to meta_data for consistency across domain models
- Update agent_identity, agent_performance, agent_portfolio, amm, analytics, bounty, certification, community, cross_chain_bridge, cross_chain_reputation, decentralized_memory, miner, pricing_models, trading, and wallet models
- Rename chain_metadata to chain_meta_data in CrossChainMapping
- Rename verification_metadata to verification_meta_data

apps/coordinator-api/src/app/config.py

@@ -5,7 +5,7 @@ Provides environment-based adapter selection and consolidated settings.
 """
 
 import os
-from pydantic import field_validator
+from pydantic import Field, field_validator
 from pydantic_settings import BaseSettings, SettingsConfigDict
 from typing import List, Optional
 from pathlib import Path