Refactor code for improved readability and consistency

- Cleaned up whitespace and formatting in various files including http.py, language.py, logger.py, safe_exec.py, and SQL migration scripts.
- Consolidated import statements and removed unnecessary blank lines.
- Updated logging configuration for better clarity.
- Enhanced the safe execution code with improved error handling and logging.
- Removed commented-out code and unnecessary variables in backfill_zero_trades.py and other scripts.
- Added a pyproject.toml for Ruff and Vulture configuration.
- Introduced requirements-dev.txt for development dependencies.
- Removed commented-out stock entries in init.sql for cleaner migration scripts.

backend_api_python/env.example

@@ -164,15 +164,10 @@ FINNHUB_TIMEOUT=10
 FINNHUB_RATE_LIMIT=60
 CCXT_DEFAULT_EXCHANGE=coinbase
 CCXT_TIMEOUT=10000
-AKSHARE_TIMEOUT=30
 YFINANCE_TIMEOUT=30
 TIINGO_API_KEY=
 TIINGO_TIMEOUT=10
 
-# Twelve Data (CN/HK stock K-lines — recommended for overseas servers)
-# Free tier: 800 API credits/day, 8 requests/minute. https://twelvedata.com
-TWELVE_DATA_API_KEY=
-
 # AI search / news
 SEARCH_PROVIDER=google
 SEARCH_MAX_RESULTS=10