Add configurable sidebar nameplate background.

Render the equipped nameplate behind the larger settings avatar with blur-aware sidebar controls, adjustable opacity, and immediate collectible cache invalidation.

src/app/state/settings.ts

@@ -50,6 +50,7 @@ export interface Settings {
   encUrlPreview: boolean;
   showHiddenEvents: boolean;
   legacyUsernameColor: boolean;
+  sidebarNameplateOpacity: number;
 
   showNotifications: boolean;
   isNotificationSounds: boolean;
@@ -93,6 +94,7 @@ const defaultSettings: Settings = {
   encUrlPreview: false,
   showHiddenEvents: false,
   legacyUsernameColor: false,
+  sidebarNameplateOpacity: 60,
 
   showNotifications: true,
   isNotificationSounds: true,