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/clustering.py

@@ -632,9 +632,8 @@ def run_clustering_analysis(df: pd.DataFrame, output_dir: "str | Path" = "output
     output_dir = Path(output_dir)
     output_dir.mkdir(parents=True, exist_ok=True)
 
-    # 设置中文字体（macOS）
-    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()
 
     print("=" * 60)
     print("  BTC 市场状态聚类与马尔可夫链分析")