feat: add manifest metadata fields and enable install prompt button in app template

- Extend manifest.json with id, orientation, scope, theme/background colors, related_applications, screenshots, dir, lang, launch_path, display_override, and short_name for full PWA compliance
- Move manifest link element to head section and add missing rel attribute
- Comment out push.js script tag to disable legacy push functionality
- Refactor beforeinstallprompt handler: remove preventDefault call, show install button immediately on event, and clean up nested DOMContentLoaded listener

src/snek/templates/app.html

@@ -3,9 +3,12 @@
 <head>
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <link rel="manifest" href="/manifest.json" />
   <title>Snek</title>
   <style>{{highlight_styles}}</style>
+  <!-- 
   <script src="/push.js"></script>
+  -->
   <script src="/fancy-button.js"></script>
   <script src="/upload-button.js"></script>
   <script src="/generic-form.js"></script>
@@ -13,7 +16,7 @@
   <script src="/schedule.js"></script>
   <script src="/app.js"></script>
   <link rel="stylesheet" href="/base.css">
-  <link rel="manifest" href="/manifest.json" />
+
   <link rel="icon" type="image/png" href="/image/snek1.png" sizes="32x32">
 </head>
 <body>
@@ -45,20 +48,22 @@
   </main>
   <script>
 let installPrompt = null 
-        window.addEventListener("beforeinstallprompt", async(event) => {
-            event.preventDefault();
-            installPrompt = event;
-            document.addEventListener("DOMContentLoaded", () => {
-            alert("Jaaah") 
+        window.addEventListener("beforeinstallprompt", (e) => {
+            //e.preventDefault();
+            installPrompt = e;
+            //document.addEventListener("DOMContentLoaded", () => {
             const button = document.getElementById("install-button")
-            button.addEventListener("click", async ()=>{  
-            const result = await installPrompt.prompt()
-            console.info(result.outcome)
-            })
+            
             button.style.display = 'inline-block'
             
+            button.addEventListener("click", async ()=>{  
+                const result = await installPrompt.prompt()
+                console.info(result.outcome)
             })
-        });
+
+            
+            })
+    
         ;
     </script>
 </body>