feat(settings): prominent sponsor banner on General tab

Matomo shows only 1.18% of website visitors reach /sponsors despite
  29% hitting /installation. The ask was discoverable on the marketing
  site but invisible in-app where users actually live.

  Full-width gradient banner sits above the three-column layout on the
  default landing tab and links to bambuddy.cool/sponsors.html with a
  ?from=app-settings tracking param so conversion lift is measurable
  in Matomo. Three new sponsors.* keys translated to all 11 locales.

static/index.html

@@ -26,8 +26,8 @@
 
     <!-- Splash screens for iOS -->
     <link rel="apple-touch-startup-image" href="/img/android-chrome-512x512.png" />
-    <script type="module" crossorigin src="/assets/index-DUIDqBr8.js"></script>
-    <link rel="stylesheet" crossorigin href="/assets/index-CEe69URA.css">
+    <script type="module" crossorigin src="/assets/index-CLr67hk0.js"></script>
+    <link rel="stylesheet" crossorigin href="/assets/index-7mua31Zk.css">
   </head>
   <body>
     <div id="root"></div>