brand identity overhaul: match BRAND-IDENTITY.md across all pages

Design system changes (per brand guide):
- ZERO rounded-2xl/3xl remaining (was 131 instances)
- ZERO bg-gradient remaining (was 25) — all solid colors
- ZERO colored shadows (shadow-trust-blue, etc) — flat, no glow
- ZERO backdrop-blur/glass effects — solid backgrounds
- ZERO emoji in logo marks — square P logomark everywhere
- ZERO decorative scale animations (group-hover:scale-105, etc)

Tailwind config:
- Added brand color names: midnight, promise-blue, generosity-gold, fulfilled-green, alert-red, paper
- Kept legacy aliases (trust-blue, etc) for backwards compat
- --radius: 0.75rem → 0.5rem (tighter corners)

CSS:
- Removed glass, glass-dark, card-hover, pulse-ring, bounce-gentle, confetti-fall, scale-in animations
- Kept only purposeful animations: fadeUp, fadeIn, slideDown, shimmer, counter-roll
- --primary tuned to match Promise Blue exactly

Components:
- Button: removed all colored shadows, added 'blue' variant, removed rounded from sizes
- All UI components: rounded-xl/2xl → rounded-lg

Pages updated (41 files):
- Dashboard layout: solid header (no blur), border-l-2 active indicator, midnight logo mark
- Login/Signup: paper bg (no gradient), midnight logo mark, no emoji
- Pledge flow: solid color icons, no gradient progress bars
- All dashboard pages: flat, sharp, editorial

pledge-now-pay-later/src/app/v/[code]/page.tsx

@@ -89,7 +89,7 @@ export default function VolunteerPage() {
 
   if (loading) {
     return (
-      <div className="min-h-screen flex items-center justify-center bg-gradient-to-br from-trust-blue/5 via-white to-warm-amber/5">
+      <div className="min-h-screen flex items-center justify-center bg-paper">
         <Loader2 className="h-8 w-8 text-trust-blue animate-spin" />
       </div>
     )
@@ -97,7 +97,7 @@ export default function VolunteerPage() {
 
   if (error || !data) {
     return (
-      <div className="min-h-screen flex items-center justify-center bg-gradient-to-br from-trust-blue/5 via-white to-warm-amber/5 p-4">
+      <div className="min-h-screen flex items-center justify-center bg-paper p-4">
         <div className="text-center space-y-4">
           <QrCode className="h-12 w-12 text-muted-foreground mx-auto" />
           <h1 className="text-xl font-bold">QR code not found</h1>
@@ -108,7 +108,7 @@ export default function VolunteerPage() {
   }
 
   return (
-    <div className="min-h-screen bg-gradient-to-br from-trust-blue/5 via-white to-warm-amber/5">
+    <div className="min-h-screen bg-paper">
       <div className="max-w-lg mx-auto px-4 py-8 space-y-6">
         {/* Header */}
         <div className="text-center space-y-2">
@@ -153,7 +153,7 @@ export default function VolunteerPage() {
             </div>
             <div className="h-3 rounded-full bg-gray-100 overflow-hidden">
               <div
-                className="h-full rounded-full bg-gradient-to-r from-trust-blue to-success-green transition-all duration-1000"
+                className="h-full rounded-full bg-promise-blue transition-all duration-1000"
                 style={{ width: `${Math.round((data.stats.totalPaidPence / data.stats.totalPledgedPence) * 100)}%` }}
               />
             </div>