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/p/[token]/loading.tsx

@@ -1,8 +1,8 @@
 export default function PledgeLoading() {
   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">
       <div className="text-center space-y-4">
-        <div className="inline-flex items-center justify-center w-16 h-16 rounded-full bg-trust-blue/10 animate-pulse">
+        <div className="inline-flex items-center justify-center w-14 h-14 bg-trust-blue/10 animate-pulse">
           <div className="w-8 h-8 rounded-full bg-trust-blue/30" />
         </div>
         <p className="text-muted-foreground animate-pulse">Loading pledge page...</p>