[FIX] fixed CJK characters rendering as □ in graphs

[EVE-Rangeen]

Summary

Graph labels and legends showed tofu (□) for Chinese, Japanese, and Korean text when using localized pyfa clients. The wx UI rendered CJK text correctly, but Matplotlib defaulted to DejaVu Sans, which lacks CJK characters.
Before Fix

After Fix

This PR adds a small Matplotlib font setup module and applies it when the graph canvas initializes Matplotlib. It builds a prioritized font stack from the system GUI font and common platform CJK fonts.
Detailed fonts per platform see below:

    if system == 'Windows':
   # Windows platform
        candidates.extend([
            'Microsoft YaHei', 'Microsoft JhengHei', 'SimHei', 'SimSun',
            'Malgun Gothic', 'Gulim', 'Dotum', 'Batang',
            'Yu Gothic', 'Meiryo', 'Arial Unicode MS',
        ])
    elif system == 'Darwin':
   # MacOS platform
        candidates.extend([
            'Apple SD Gothic Neo', 'AppleGothic', 'PingFang SC', 'PingFang TC',
            'Hiragino Sans GB', 'Hiragino Sans', 'Heiti SC', 'Arial Unicode MS',
        ])
    else:
   # Linux platform
        candidates.extend([
            'NanumGothic', 'UnDotum', 'WenQuanYi Micro Hei', 'WenQuanYi Zen Hei',
            'Droid Sans Fallback',
        ])
   # DejaVu Sans (Default Matplotlib font as final fallback font) for English letters, numbers, and symbols.
     candidates.append('DejaVu Sans')   

Then assigns it to font.family so Matplotlib 3.6+ can fall back per glyph. Hence mixed legend text also works (e.g. Chinese shipname in Japanese/Korean GUI), see above.

Changes

• Add graphs/mpl_fonts.py with configure_matplotlib_font()
• Call it from graphs/gui/canvasPanel.py after mpl.use('wxagg')

##P.S.
I did some manual tests myself on windows, it looks pretty good, but I dont have any macOS or linux device, so I cant test on these platforms