feat: Phase 4 Aether Drift — auth, modals & UI component token migration

Migrate all auth pages, modals, and shared UI components from Discord
visual language to Aether Drift design tokens. Zero discord-* classes
or raw Tailwind palette colors remain in components/auth/, modals/, ui/.

- Avatar: status dots use status-online/idle/dnd/offline tokens
- Tooltip, ContextMenu, UserProfilePopout: z-index raised to z-[200]
- LoginPage, RegisterPage: warm bg-surface-base with lavender glow
- All modals: inputs use surface-input, buttons use accent-primary
- Toggles: bg-status-online (on), bg-surface-input (off)
- ServerSettings: slider tracks, pills, danger zone fully tokenized
- Purged raw Tailwind green-500 leak in StreamingLimitsPanel success msg

packages/web/src/components/modals/JoinServer.tsx

@@ -48,23 +48,23 @@ export function JoinServerModal() {
   return (
     <Modal isOpen={isOpen} onClose={closeModal} title="Join a Server">
       <form onSubmit={handleSubmit}>
-        <p className="text-discord-text-secondary text-sm mb-4">
+        <p className="text-txt-secondary text-sm mb-4">
           Enter an invite code to join an existing server.
         </p>
         {error && (
-          <div className="mb-3 p-2 bg-discord-red/10 border border-discord-red/30 rounded text-discord-text-danger text-sm">
+          <div className="mb-3 p-2 bg-accent-rose/10 border border-accent-rose/30 rounded text-txt-danger text-sm">
             {error}
           </div>
         )}
         <div className="mb-4">
-          <label className="block text-xs font-bold text-discord-text-secondary uppercase mb-2">
+          <label className="block text-xs font-bold text-txt-secondary uppercase mb-2">
             Invite Code
           </label>
           <input
             type="text"
             value={inviteCode}
             onChange={(e) => setInviteCode(e.target.value)}
-            className="w-full px-3 py-2 bg-discord-bg-tertiary rounded text-discord-text-primary outline-none focus:ring-2 focus:ring-discord-blurple"
+            className="w-full px-3 py-2 bg-surface-input rounded text-txt-primary outline-none focus:ring-2 focus:ring-accent-primary"
             placeholder="e.g. abc123"
             autoFocus
           />
@@ -73,14 +73,14 @@ export function JoinServerModal() {
           <button
             type="button"
             onClick={closeModal}
-            className="px-4 py-2 text-sm text-discord-text-secondary hover:text-discord-text-primary transition-colors"
+            className="px-4 py-2 text-sm text-txt-secondary hover:text-txt-primary transition-colors"
           >
             Cancel
           </button>
           <button
             type="submit"
             disabled={isLoading}
-            className="px-4 py-2 bg-discord-blurple hover:bg-discord-blurple-hover text-white text-sm font-medium rounded transition-colors disabled:opacity-50"
+            className="px-4 py-2 bg-accent-primary hover:bg-accent-primary/80 text-white text-sm font-medium rounded transition-colors disabled:opacity-50"
           >
             {isLoading ? 'Joining...' : 'Join Server'}
           </button>