feat: print page with crop editor and live sheet preview

New Druck tab: upload or pick from the library, choose a target size and copy
count per image, pan/zoom crop on a locked aspect ratio, and a live preview
that renders the same layout the PDF will contain. Sheet controls for paper,
margin, gap, bleed, crop marks, dpi and templates.

src/layouts/Base.astro

@@ -14,6 +14,7 @@ const active = (href: string) => href === '/' ? path === '/' : path.startsWith(h
 const nav = [
   { href: '/', label: 'Studio', icon: 'studio' },
   { href: '/bibliothek', label: 'Bibliothek', icon: 'library' },
+  { href: '/druck', label: 'Druck', icon: 'print' },
   { href: '/warteschlange', label: 'Warteschlange', icon: 'queue' },
   { href: '/anleitung', label: 'Hilfe', icon: 'help' },
   ...(user?.role === 'admin' ? [{ href: '/admin', label: 'Admin', icon: 'admin' }] : []),
@@ -25,6 +26,7 @@ const ICONS: Record<string, string> = {
   library: `<svg viewBox="0 0 24 24" ${S}><rect x="3.5" y="3.5" width="7" height="7" rx="1.5"/><rect x="13.5" y="3.5" width="7" height="7" rx="1.5"/><rect x="3.5" y="13.5" width="7" height="7" rx="1.5"/><rect x="13.5" y="13.5" width="7" height="7" rx="1.5"/></svg>`,
   queue: `<svg viewBox="0 0 24 24" ${S}><path d="M9 6h11M9 12h11M9 18h7"/><circle cx="4.5" cy="6" r="1.15" fill="currentColor" stroke="none"/><circle cx="4.5" cy="12" r="1.15" fill="currentColor" stroke="none"/><circle cx="4.5" cy="18" r="1.15" fill="currentColor" stroke="none"/></svg>`,
   admin: `<svg viewBox="0 0 24 24" ${S}><path d="M4 8h9M17 8h3M4 16h3M11 16h9"/><circle cx="15" cy="8" r="2.2"/><circle cx="9" cy="16" r="2.2"/></svg>`,
+  print: `<svg viewBox="0 0 24 24" ${S}><path d="M7 9V4.5h10V9"/><rect x="3.5" y="9" width="17" height="7" rx="2"/><path d="M7 14h10v5.5H7z"/></svg>`,
   help: `<svg viewBox="0 0 24 24" ${S}><circle cx="12" cy="12" r="8.5"/><path d="M9.6 9.4a2.5 2.5 0 1 1 3.4 2.3c-.7.3-1 .8-1 1.6v.3"/><circle cx="12" cy="16.7" r="0.6" fill="currentColor" stroke="none"/></svg>`,
 };
 ---