feat(badges): layout CSS system — data-layout attribute, @page injection, style_href

Two compiled layout CSS files in src/lib/ae_events/badges/css/:
  - badge_layout_epson_4x5_fanfold.css — 4"×5" per side, Epson ColorWorks C3500
    fanfold duplex; preferred for general conference use (ISHLT, demos)
  - badge_layout_zebra_zc10l_pvc.css — 3.5"×5.5" PVC card, Zebra ZC10L,
    single-sided (pair with duplex=0 on template)

Rules scoped under [data-layout="..."] on the wrapper — beats Tailwind utility
class specificity without !important. Vite hot-reloads these in dev.

Badge component: add data-layout attribute from template.layout field; import
both layout CSS files (falls back to Tailwind 4"×6" defaults if layout unset).

Print page svelte:head: inject @page paper-size rule per layout code
(@page cannot use attribute selectors so it must be dynamic). Also wire
style_href as a <link> for per-event external client branding CSS.

db_events.ts Badge_template interface: add style_href and duplex fields.
MODULE doc: update layout codes table with badge_4x5_fanfold entry.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/ae_events/db_events.ts

@@ -251,6 +251,8 @@ export interface Badge_template {
 
     layout?: null | string;
     style_filename?: null | string;
+    style_href?: null | string;
+    duplex?: null | number | boolean;
 
     enable?: null | boolean;
     hide?: null | boolean;