add web app manifest so site can be installed as a desktop app (v4)

Adds manifest.json + a 512x512 icon and links them from layout.njk, so
Edge/Chrome can install the site as a standalone app window from a
desktop shortcut while it keeps loading live from the server.

RELEASE_NOTES.md

@@ -1,5 +1,11 @@
 # Release Notes
 
+## v4 — 2026-07-18
+
+- Added a web app manifest (`manifest.json`) and a 512x512 icon, so the site
+  can be installed as a desktop app from Edge/Chrome — opens in its own
+  window instead of a browser tab, while still loading live from the server.
+
 ## v3 — 2026-07-16
 
 - Added a favicon (clock + "H" mark), with a transparent icon set for

public/manifest.json

@@ -0,0 +1,12 @@
+{
+  "name": "Harding's Service",
+  "short_name": "Harding's Service",
+  "start_url": "/",
+  "display": "standalone",
+  "background_color": "#F2E8D5",
+  "theme_color": "#4A2810",
+  "icons": [
+    { "src": "/icons/icon-192.png", "sizes": "192x192", "type": "image/png" },
+    { "src": "/icons/icon-512.png", "sizes": "512x512", "type": "image/png" }
+  ]
+}

src/views/layout.njk

@@ -9,6 +9,8 @@
   <link rel="icon" type="image/png" sizes="32x32" href="/icons/favicon-32x32.png">
   <link rel="icon" type="image/png" sizes="192x192" href="/icons/icon-192.png">
   <link rel="apple-touch-icon" href="/icons/apple-touch-icon.png">
+  <link rel="manifest" href="/manifest.json">
+  <meta name="theme-color" content="#4A2810">
   <link rel="stylesheet" href="/css/style.css">
   <script src="/vendor/htmx/htmx.min.js" defer></script>
 </head>