feat: add display kiosk host

surfaces/shell/display.html

@@ -0,0 +1,14 @@
+<!doctype html>
+<html lang="en" style="height: 100%; margin: 0; overflow: hidden">
+  <head>
+    <meta charset="utf-8" />
+    <meta content="width=device-width, initial-scale=1" name="viewport" />
+    <title>Display</title>
+  </head>
+  <body style="height: 100%; margin: 0; overflow: hidden">
+    <!-- Structural canvas only. The module owns every visible pixel after mounting. -->
+    <div id="ekklesia-display" style="height: 100%; min-height: 100dvh; overflow: hidden"></div>
+    <!-- Fixed host asset, never a module-derived path and never an inline bootstrap script. -->
+    <script src="/assets/ekklesia-display/app.js" type="module"></script>
+  </body>
+</html>