Badges: fix print centering — dissolve .main_content; hide footer/scroll buttons from print; document print layout architecture

src/routes/events/+layout.svelte

@@ -282,6 +282,7 @@
     <div
         class:hidden={yTop < 500}
         class="
+        print:hidden
         z-20
         hover:opacity-100
         fixed bottom-40 right-1
@@ -356,8 +357,7 @@
             class:opacity-80={yTop < 250}
             class:opacity-0={yTop > 250}
             class="
-        footer
-        z-20
+        footer        print:hidden        z-20
         hover:opacity-100
         absolute bottom-0 left-0 right-0
         w-full max-w-7xl

src/routes/events/[event_id]/(badges)/badges/[badge_id]/print/+page.svelte

@@ -183,8 +183,14 @@
             /* Dissolve layout wrappers — removes their boxes from the layout while
                keeping children renderable. The badge section floats up to body
                as a direct flex child, so body's centering applies to it directly.
-               This avoids all height-chain and overflow-clip issues. */
+               This avoids all height-chain and overflow-clip issues.
+
+               Layers dissolved:
+                 #ae_main_content  — events layout scroll container (flex-col, max-w-7xl, overflow-auto, bg-gray)
+                 .main_content     — events layout inner section (grow, pb-48, pt-20+, items-center)
+                 #badge_render_area — print page badge wrapper (screen-only right padding) */
             #ae_main_content,
+            .main_content,
             #badge_render_area {
                 display: contents !important;
             }