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/config/settings.cpp

@@ -204,6 +204,8 @@ bool Settings::load(const std::string& path)
             ui_opacity_ = 1.0f; // legacy: reduced = fully opaque
         }
         loadScalar(j, "window_opacity", window_opacity_);
+        loadScalar(j, "favorite_opacity", favorite_opacity_);
+        favorite_opacity_ = std::clamp(favorite_opacity_, 0.15f, 1.0f);   // matches setFavoriteOpacity()
         if (j.contains("balance_layout")) {
             if (j["balance_layout"].is_string())
                 balance_layout_ = j["balance_layout"].get<std::string>();
@@ -542,6 +544,7 @@ bool Settings::save(const std::string& path)
     j["gradient_background"] = gradient_background_;
     j["ui_opacity"] = ui_opacity_;
     j["window_opacity"] = window_opacity_;
+    j["favorite_opacity"] = favorite_opacity_;
     j["balance_layout"] = balance_layout_;  // saved as string ID
     j["portfolio_style"] = portfolio_style_;
     j["contacts_view_mode"] = contacts_view_mode_;