fix: Enforce environment proxy trust for ccxt.pro market data source

[byronwang2005]

📝 Pull Request Template

1. Related Issue

Closes #495

2. Type of Change (select one)

Type of Change: Bug Fix

3. Description

Summary

• Enable aiohttp_trust_env=True when instantiating ccxt.pro exchange objects, allowing environment variables such as HTTP_PROXY, HTTPS_PROXY, ALL_PROXY, and NO_PROXY to take effect for market data fetching.
• Unify proxy behavior across REST/WS asynchronous channels, resolving timeout or direct-connection failures for calls like fetch_ohlcv and fetch_ticker in proxy-requiring network environments.

Motivation & Background

• aiohttp by default ignores system proxy environment variables, causing ccxt.pro’s async requests to fail in environments where proxies are required for external API access.
• Enabling aiohttp_trust_env allows ccxt.pro to transparently respect proxy settings from .env files or process environments—no need to manually inject proxy config per call.

4. Testing

• I have tested this locally.
• I have updated or added relevant tests.

5. Checklist

• I have read the Code of Conduct
• I have followed the Contributing Guidelines
• My changes follow the project's coding style