feat(ui): PageHeader/PageContainer foundation (piloted on Contacts); profile info-first on mobile

- New shared PageHeader + PageContainer (width tokens: narrow/list/detail/wide)
  to end the max-w drift between sections; piloted on ContactsPage
- Profile: the identity/contact sidebar now comes first on mobile (order-first /
  lg:order-none) instead of being buried under every content section

src/components/PageHeader.tsx

@@ -0,0 +1,66 @@
+import type { ComponentType, ReactNode } from 'react';
+import { cn } from '@/lib/utils';
+
+/**
+ * Shared page header + width tokens (UX foundations).
+ *
+ * Pages previously each hand-rolled their own title markup and container
+ * width (max-w-2xl / -3xl / -4xl / -7xl / unbounded), so navigating between
+ * sections felt like moving between different apps. New/edited pages should
+ * use these; existing pages can be migrated incrementally.
+ */
+export function PageHeader({
+  title,
+  subtitle,
+  icon: Icon,
+  accent = '#ccff00',
+  actions,
+  className,
+}: {
+  title: ReactNode;
+  subtitle?: ReactNode;
+  icon?: ComponentType<{ className?: string }>;
+  /** Title colour. Defaults to the app's lime accent. */
+  accent?: string;
+  actions?: ReactNode;
+  className?: string;
+}) {
+  return (
+    <div className={cn('mb-5 flex items-start justify-between gap-3', className)}>
+      <div className="min-w-0">
+        <h1
+          className="flex items-center gap-2 text-3xl font-black uppercase leading-none sm:text-4xl"
+          style={{ color: accent, fontFamily: 'Impact, "Arial Black", sans-serif' }}
+        >
+          {Icon && <Icon className="h-7 w-7 shrink-0 sm:h-8 sm:w-8" />}
+          <span className="truncate">{title}</span>
+        </h1>
+        {subtitle && <p className="mt-2 text-sm text-gray-400">{subtitle}</p>}
+      </div>
+      {actions && <div className="flex shrink-0 items-center gap-2">{actions}</div>}
+    </div>
+  );
+}
+
+const WIDTHS = {
+  narrow: 'max-w-2xl',
+  list: 'max-w-3xl',
+  detail: 'max-w-4xl',
+  wide: 'max-w-7xl',
+} as const;
+
+export function PageContainer({
+  children,
+  width = 'detail',
+  className,
+}: {
+  children: ReactNode;
+  width?: keyof typeof WIDTHS;
+  className?: string;
+}) {
+  return (
+    <div className={cn('container mx-auto px-4 py-6', WIDTHS[width], className)}>
+      {children}
+    </div>
+  );
+}

src/pages/ContactsPage.tsx

@@ -3,6 +3,7 @@ import { useSeoMeta } from '@unhead/react';
 import { Link } from 'react-router-dom';
 import { nip19 } from 'nostr-tools';
 import { Layout } from '@/components/Layout';
+import { PageHeader } from '@/components/PageHeader';
 import { Card, CardContent } from '@/components/ui/card';
 import { Button } from '@/components/ui/button';
 import { Skeleton } from '@/components/ui/skeleton';
@@ -221,17 +222,12 @@ export default function ContactsPage() {
     <Layout>
       <div className="container max-w-2xl px-4 py-6">
         {/* Header */}
-        <div className="mb-4">
-          <h1
-            className="flex items-center gap-2 text-3xl font-black uppercase text-teal-400"
-            style={{ fontFamily: 'Impact, "Arial Black", sans-serif' }}
-          >
-            <Users className="h-7 w-7" /> Contacts
-          </h1>
-          <p className="mt-1 text-sm text-gray-400">
-            Your scene — crew-mates, follows &amp; conversations
-          </p>
-        </div>
+        <PageHeader
+          title="Contacts"
+          icon={Users}
+          accent="#2dd4bf"
+          subtitle="Your scene — crew-mates, follows &amp; conversations"
+        />
 
         {/* Search */}
         <div className="relative mb-4">

src/pages/NIP19Page.tsx

@@ -706,7 +706,9 @@ function ProfilePage({ pubkey }: { pubkey: string }) {
           </div>
 
           {/* Sidebar */}
-          <div className="space-y-4 min-w-0">
+          {/* On mobile the identity/contact cards come first — the info card was
+              previously buried below every content section on phones. */}
+          <div className="space-y-4 min-w-0 order-first lg:order-none">
             {/* Zap achievements (only renders when this profile has sent zaps) */}
             <ZapBadgesCard pubkey={pubkey} />