feat: unified glass material system for all floating surfaces

Add .glass-modal CSS class (0.82 opacity) for dialogs and apply
consistent glass tiers across all floating UI: modals, context menus,
tooltips, popovers, and call cards. Replaces ad-hoc bg-surface-elevated
and inline styles with the documented 5-tier glass hierarchy.

packages/web/src/components/ui/Modal.tsx

@@ -27,10 +27,10 @@ export function Modal({ isOpen, onClose, title, children, maxWidth = 'max-w-md'
   return (
     <div className="fixed inset-0 z-[200] flex items-center justify-center animate-fade-in">
       <div
-        className="absolute inset-0 bg-surface-overlay"
+        className="absolute inset-0 bg-black/50"
         onClick={onClose}
       />
-      <div className={`relative ${maxWidth} w-full mx-4 max-h-[calc(100vh-2rem)] flex flex-col bg-surface-elevated rounded-lg shadow-xl animate-slide-up`}>
+      <div className={`relative ${maxWidth} w-full mx-4 max-h-[calc(100vh-2rem)] flex flex-col glass-modal rounded-lg animate-slide-up`}>
         {title && (
           <div className="flex items-center justify-between px-4 pt-4 flex-shrink-0">
             <h2 className="text-xl font-bold text-txt-primary">{title}</h2>