style: simplify app icon branding

public/icons/icon.svg

@@ -1,12 +1,6 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512">
-  <defs>
-    <linearGradient id="g" x1="70" y1="44" x2="450" y2="484" gradientUnits="userSpaceOnUse">
-      <stop stop-color="#38bdf8"/>
-      <stop offset=".52" stop-color="#2563eb"/>
-      <stop offset="1" stop-color="#312e81"/>
-    </linearGradient>
-  </defs>
-  <rect width="512" height="512" rx="142" fill="url(#g)"/>
-  <circle cx="388" cy="138" r="78" fill="#fff" fill-opacity=".12"/>
-  <text x="62" y="318" fill="white" font-family="Arial, Helvetica, sans-serif" font-size="186" font-weight="700" letter-spacing="-28">wtr.</text>
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" role="img" aria-label="wtr.">
+  <rect width="512" height="512" rx="120" fill="#171d25"/>
+  <rect x="22" y="22" width="468" height="468" rx="102" fill="none" stroke="#eef3f7" stroke-opacity=".16" stroke-width="2"/>
+  <text x="62" y="318" fill="#eef3f7" font-family="Arial, Helvetica, sans-serif" font-size="186" font-weight="700" letter-spacing="-28">wtr</text>
+  <circle cx="382" cy="295" r="18" fill="#8fb4ce"/>
 </svg>