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/Resources/HellionStrings.Designer.cs

@@ -136,4 +136,6 @@ internal class HellionStrings
     internal static string Theme_Enabled_Description => Get(nameof(Theme_Enabled_Description));
     internal static string Theme_WindowOpacity_Label => Get(nameof(Theme_WindowOpacity_Label));
     internal static string Theme_WindowOpacity_Help => Get(nameof(Theme_WindowOpacity_Help));
+    internal static string Theme_UseHellionFont_Name => Get(nameof(Theme_UseHellionFont_Name));
+    internal static string Theme_UseHellionFont_Description => Get(nameof(Theme_UseHellionFont_Description));
 }