feat(07.1-frontend-overhaul): refine StatCard and Data Tables

- Applied #121212 background and #222222 border to StatCards and Tables.
- Tightened internal padding to 8px-12px.
- Enforced 0px border radius and removed shadows.
- Numeric values in StatCards now match label size.
- Caution Orange used for emphasis in StatCards.
- Removed zebra-striping and applied 1px horizontal dividers to Tables.
- Headers updated to Title Case Space Grotesk.
- Complies with AI_RULES.md (no bold, no uppercase).

frontend/components/StatCard.tsx

@@ -9,7 +9,7 @@ interface StatCardProps {
 
 export default function StatCard({ label, value, icon: Icon }: StatCardProps) {
   return (
-    <div className="flex justify-between items-center gap-2 p-3 lg:p-4 xl:p-5 lg:p-6 xl:p-8.5 bg-surface/70 border border-slate-800/50 rounded-2xl shadow-sm transition-all hover:bg-surface" role="status">
+    <div className="flex justify-between items-center gap-2 p-2 md:p-3 bg-surface-container border border-border transition-all hover:bg-surface-bright" role="status">
       <div className="flex items-center gap-2.5 min-w-0">
         {Icon && <Icon className="w-5 h-5 text-primary flex-shrink-0" aria-hidden="true" />}
         <span className="text-base md:text-lg text-secondary font-normal truncate">
@@ -17,7 +17,7 @@ export default function StatCard({ label, value, icon: Icon }: StatCardProps) {
         </span>
       </div>
 
-      <span className="text-base md:text-lg font-normal text-white whitespace-nowrap tabular-nums">
+      <span className="text-base md:text-lg font-normal text-primary whitespace-nowrap tabular-nums">
         {value}
       </span>
     </div>