feat: add foodsharing manager branding

Add supplied logos, favicons, PWA metadata, branded login and navigation,
and apply the Foodsharing Manager green palette across existing views.

images/foodsharing-manager-logo-assets/pwa/site.webmanifest

@@ -0,0 +1,27 @@
+{
+  "name": "Foodsharing Manager",
+  "short_name": "FS Manager",
+  "icons": [
+    {
+      "src": "/pwa/android-chrome-192x192.png",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "any"
+    },
+    {
+      "src": "/pwa/android-chrome-512x512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "any"
+    },
+    {
+      "src": "/pwa/maskable-icon-512x512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "maskable"
+    }
+  ],
+  "theme_color": "#248A3D",
+  "background_color": "#F7FBF5",
+  "display": "standalone"
+}