web: logo on the login page, icon as favicon and in the headers

public/logo.png is the source; icon-192.png (the mark, cropped and padded
on the logo's background) and logo-512.png (login card) are cut from it
with ffmpeg so pages don't load the 1.2 MB original. Brand (icon + name)
replaces the plain app name in the admin and My Phone headers.

apps/web/index.html

@@ -4,6 +4,8 @@
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>SelfPhoneNG</title>
+    <link rel="icon" type="image/png" href="/icon-192.png" />
+    <link rel="apple-touch-icon" href="/icon-192.png" />
     <script>
       // Apply the theme before first paint so dark mode doesn't flash.
       try {