Bundle the Hellion icon and Exo 2 font

Replace the inherited Chat 2 icon with the 1024×1024 Hellion logo
from the Hellion Online Media brand assets so the plugin shows
its real identity in Dalamud's plugin list. Bundle Exo 2 Variable
(SIL Open Font License 1.1) as an embedded resource together with
the OFL license text — keeps the license travelling with the font
inside the assembly as the OFL requires.

A new Configuration.UseHellionFont (default true) plus a checkbox
in the Privacy tab Appearance section route FontManager's regular
font handle through tk.AddFontFromMemory using the embedded TTF
bytes when the toggle is on; flipping it off falls back to the
existing AddFontWithFallback path so users who picked their own
system font under Settings → Fonts keep that choice.

Settings.cs now treats UseHellionFont as a font-changing setting
so toggling it triggers FontManager.BuildFonts on save without
needing a plugin reload.

ChatTwo/Ui/Settings.cs

@@ -156,7 +156,8 @@ public sealed class SettingsWindow : Window
         var fontChanged = Mutable.GlobalFontV2 != Plugin.Config.GlobalFontV2
                           || Mutable.JapaneseFontV2 != Plugin.Config.JapaneseFontV2
                           || Mutable.ItalicFontV2 != Plugin.Config.ItalicFontV2
-                          || Mutable.ExtraGlyphRanges != Plugin.Config.ExtraGlyphRanges;
+                          || Mutable.ExtraGlyphRanges != Plugin.Config.ExtraGlyphRanges
+                          || Mutable.UseHellionFont != Plugin.Config.UseHellionFont;
         var fontSizeChanged = Math.Abs(Mutable.SymbolsFontSizeV2 - Plugin.Config.SymbolsFontSizeV2) > 0.001
                           || Math.Abs(Mutable.FontSizeV2 - Plugin.Config.FontSizeV2) > 0.001;
         var italicStateChanged = Mutable.ItalicEnabled != Plugin.Config.ItalicEnabled;