Refactor repo structure and add new icon sets

Restructured the repository from v1-v4 folders to a set-based organization
(set-1 through set-6) grouped by visual style rather than arbitrary version
numbers. Added new icon sets, dark theme variants, Lottie animations, and
a comprehensive icons.json mapping file.

sets/set-3/light/mixed_rain_hail_sleet.svg

@@ -0,0 +1,20 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32">
+  <defs>
+    <linearGradient id="a" x1="22.493%" x2="100%" y1="17.395%" y2="115.202%">
+      <stop offset="0%" stop-color="#F1F3F4"/>
+      <stop offset="100%" stop-color="#DEDFDF"/>
+    </linearGradient>
+    <linearGradient id="b" x1="100%" x2="50%" y1="100%" y2="100%">
+      <stop offset="0%" stop-color="#FFF"/>
+      <stop offset="100%" stop-color="#F1F3F4"/>
+    </linearGradient>
+  </defs>
+  <g fill="none" fill-rule="evenodd">
+    <circle cx="20" cy="12" r="12" fill="#F1F3F4"/>
+    <circle cx="20" cy="12" r="12" fill="url(#a)"/>
+    <path fill="url(#b)" d="M20 24c0-5.523-4.477-10-10-10S0 18.477 0 24c.015-.023 20.005-.015 20 0Z"/>
+    <path fill="#4285F4" d="M16 19h1v5h-1zm2 0h1v5h-1zm2 0h1v5h-1z"/>
+    <circle cx="3" cy="3" r="2.5" stroke="#4285F4" transform="translate(25 26)"/>
+    <path fill="#4285F4" d="M26.268 11.768 28.036 10l1.767 1.768a2.5 2.5 0 1 1-3.535 0Z"/>
+  </g>
+</svg>