Fix Chinese font rendering in all chart outputs

- Add src/font_config.py: centralized font detection that auto-selects
  from Noto Sans SC > Hiragino Sans GB > STHeiti > Arial Unicode MS
- Replace hardcoded font lists in all 18 modules with unified config
- Add .gitignore for __pycache__, .DS_Store, venv, etc.
- Regenerate all 70 charts with correct Chinese rendering

Previously, 7 modules (fft, wavelet, acf, fractal, hurst, indicators,
patterns) had no Chinese font config at all, causing □□□ rendering.
The remaining 11 modules used a hardcoded fallback list that didn't
prioritize the best available system font.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/volume_price_analysis.py

@@ -15,9 +15,8 @@ from statsmodels.tsa.stattools import grangercausalitytests
 from pathlib import Path
 from typing import Dict, List, Tuple
 
-# 中文显示支持
-plt.rcParams['font.sans-serif'] = ['Arial Unicode MS', 'SimHei', 'DejaVu Sans']
-plt.rcParams['axes.unicode_minus'] = False
+from src.font_config import configure_chinese_font
+configure_chinese_font()
 
 
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