feat: Discord Dark theme overhaul — darker palette, floating controls, UI polish

Shift entire color palette from Discord's Ash theme to the darker Dark theme.
Redesign VoiceControlBar as floating auto-show pill, add gradient Join Voice
screen, move invite icon to server header, add voice channel user status
badges, update auth pages with subtle gradient backgrounds, and sweep all
hardcoded hex colors across 14 files to match the new darker palette.

packages/web/src/styles/globals.css

@@ -31,11 +31,11 @@
   }
 
   ::-webkit-scrollbar-thumb {
-    @apply bg-[#1a1b1e] rounded-full border-2 border-transparent bg-clip-padding;
+    @apply bg-[#111214] rounded-full border-2 border-transparent bg-clip-padding;
   }
 
   ::-webkit-scrollbar-thumb:hover {
-    @apply bg-[#27282c];
+    @apply bg-[#1a1b1e];
   }
 
   .no-scrollbar::-webkit-scrollbar {
@@ -47,7 +47,7 @@
   input:-webkit-autofill:hover,
   input:-webkit-autofill:focus {
     -webkit-text-fill-color: #ffffff;
-    -webkit-box-shadow: 0 0 0px 1000px #1e1f22 inset;
+    -webkit-box-shadow: 0 0 0px 1000px #111214 inset;
     transition: background-color 5000s ease-in-out 0s;
   }
 }
@@ -89,3 +89,12 @@
 .animate-slide-up {
   animation: slideUp 0.15s ease-out;
 }
+
+@keyframes gradientPulse {
+  0%, 100% { opacity: 0.7; }
+  50% { opacity: 1; }
+}
+
+.animate-gradient-pulse {
+  animation: gradientPulse 4s ease-in-out infinite;
+}