feat(settings): adjustable opacity for the favorite gold outline + star

Adds a "Favorite Highlight Opacity" slider (15-100%, default 100%) to
Settings > Appearance > Scale & Effects. It scales the alpha of the four
favorite gold tokens (fill/border/icon/outline) at their resolve site in
the Balance address list via material::ScaleAlpha, so the gold row outline
and the star button fade together. The multiplier is skin-agnostic (it
scales whatever alpha the theme resolved) and touches only favorited rows;
non-favorite rows and the white selection highlight are unchanged, and the
100% default is byte-identical to the previous look.

The preference lives in Settings (favorite_opacity, clamped 0.15-1.0 in both
the setter and on load), persists across restarts, updates live, and is not
low-spec gated (it's a pure color-alpha preference, independent of the
transparency sliders). New i18n keys favorite_opacity / tt_favorite_opacity
are translated into all eight locales; the CJK subset font is rebuilt to add
the two new glyphs the zh string needs.

Verified: full + lite builds clean, full + lite test suites pass, hygiene OK.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/util/i18n.cpp

@@ -520,6 +520,7 @@ void I18n::loadBuiltinEnglish()
         strings_["noise"] = "Noise";
         strings_["ui_opacity"] = "UI Opacity";
         strings_["window_opacity"] = "Window Opacity";
+        strings_["favorite_opacity"] = "Favorite Highlight Opacity";
         strings_["font_scale"] = "Font Scale";
         strings_["refresh"] = "Refresh";
         strings_["website"] = "Website";
@@ -795,6 +796,7 @@ void I18n::loadBuiltinEnglish()
         strings_["tt_noise"] = "Grain texture intensity (0% = off, 100% = maximum)";
         strings_["tt_ui_opacity"] = "Card and sidebar opacity (100% = fully opaque, lower = more see-through)";
         strings_["tt_window_opacity"] = "Background opacity (lower = desktop visible through window)";
+        strings_["tt_favorite_opacity"] = "Opacity of the favorite star button and its gold outline in the address list (minimum 15%)";
         strings_["tt_font_scale"] = "Scale all text and UI (1.0x = default, up to 1.5x). Hotkey: Alt + Scroll Wheel";
         strings_["tt_custom_theme"] = "Custom theme active";
         strings_["tt_address_book"] = "Manage saved addresses for quick sending";