fix(ui): apply the saved appearance settings at startup

Low-spec mode, theme effects, blur, UI and noise opacity and the
console scanline reached the live effects state only once the Settings
page or the first-run wizard was opened. "Effects off" and low-spec
therefore reverted at every launch, and the animated defaults kept the
main loop busy (91% of a core on an idle Lite wallet whose effects were
saved off).

- App::applyVisualSettings(): one low-spec-aware path from the saved
  prefs to the effects state, used at startup (after the skin, since
  setActiveSkin reloads the effect config), by the low-spec hotkey, the
  wizard and the Settings page.
- Low-spec stays a runtime-only override. The Settings page shows the
  overrides but persists the real prefs from its snapshot, and opening
  it under low-spec no longer turns theme effects and blur back on.
  Unticking a low-spec in the wizard that was loaded rather than ticked
  there now restores the saved prefs.
- Theme effects on/off always pairs with reduced transparency (the
  rainbow, shimmer and glare layers), as at startup and in the hotkeys.
- kAcrylicMaxBlur moves to imgui_acrylic.h, so startup clamps blur
  values saved in the old 0-4 range the way the slider does.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app.h

@@ -125,6 +125,14 @@ public:
     float logicDeltaTime() const { return logic_dt_; }
     static constexpr float kMaxLogicDeltaSeconds = 6.0f;
 
+    /**
+     * @brief Push the saved appearance prefs (low-spec, theme effects, blur, UI and noise opacity,
+     * console scanline) to the live effects state. Low-spec overrides the rest without touching the
+     * saved values. Called at startup, by the low-spec hotkey, the first-run wizard and the Settings
+     * page, so every path applies the same thing.
+     */
+    void applyVisualSettings();
+
     /**
      * @brief Pre-frame tasks that must run BEFORE ImGui::NewFrame().
      *