Add favicon: inline SVG panel+dot icon matching the nav brand mark, no asset file needed

web/templates/base.html

@@ -4,6 +4,10 @@
   <meta charset="utf-8">
   <meta name="viewport" content="width=device-width, initial-scale=1">
   <title>Paperwall</title>
+  <!-- Inline SVG favicon, no static asset needed: a dark panel frame with a
+       light "screen" inset and the same dot used as the brand mark in the
+       nav ("● Paperwall") -- a little wall-mounted display, on brand. -->
+  <link rel="icon" type="image/svg+xml" href="data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 32 32'><rect width='32' height='32' rx='7' fill='%23121212'/><rect x='6' y='6' width='20' height='20' rx='3' fill='%23f2f2f0'/><circle cx='10' cy='10' r='2.2' fill='%23121212'/></svg>">
   <style>
     /* Dark mode only, no light theme -- doesn't follow prefers-color-scheme. */
     :root {