feat(brand): default favicon emblem + Powered By footer badge

Ship the Runic Gateway emblem as the baked-in default favicon so an
instance renders a tab icon with no BRAND_FAVICON set, and place a
left-justified "Powered By" badge in the site footer.

- brand.favicon now defaults to /assets/img/favicon.ico (was empty).
  BRAND_FAVICON still overrides per-instance.
- Add favicon.ico + powered-by.svg under client/public/assets/img.
- SiteFooter: badge pinned to the left of the centered content column
  (absolute on >=641px, stacked on mobile); info text stays centered.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XmHdsbnLzDMAVQkAoTQSBe

client/src/components/SiteFooter.jsx

@@ -5,31 +5,37 @@ export default function SiteFooter() {
   const { contactEmail, siteTitle } = useSite()
   return (
     <footer
-      className="sans"
+      className="sans site-footer"
       style={{
         borderTop: '1px solid var(--line)',
         padding: '28px 16px',
         color: 'var(--muted)',
-        textAlign: 'center',
         fontSize: '0.9rem',
         background: 'rgba(9,13,18,0.6)',
       }}
     >
-      <div style={{ display: 'flex', flexDirection: 'column', alignItems: 'center', gap: 6 }}>
-        <span>{siteTitle} is an independent private shard project.</span>
-        <span style={{ color: 'var(--dim)', fontSize: '0.84rem' }}>
-          <a href={`mailto:${contactEmail}`} style={{ color: 'var(--accent)', textDecoration: 'none' }}>
-            {contactEmail}
-          </a>
-          &nbsp;·&nbsp;
-          <Link to="/site/status" style={{ color: 'var(--accent)', textDecoration: 'none' }}>
-            Shard Status
-          </Link>
-          &nbsp;·&nbsp;
-          <Link to="/admin/login" style={{ color: '#5d6b7d', textDecoration: 'none' }}>
-            Admin
-          </Link>
-        </span>
+      <div className="site-footer-inner">
+        <img
+          className="site-footer-badge"
+          src="/assets/img/powered-by.svg"
+          alt="Powered by Runic Gateway"
+        />
+        <div className="site-footer-info">
+          <span>{siteTitle} is an independent private shard project.</span>
+          <span style={{ color: 'var(--dim)', fontSize: '0.84rem' }}>
+            <a href={`mailto:${contactEmail}`} style={{ color: 'var(--accent)', textDecoration: 'none' }}>
+              {contactEmail}
+            </a>
+            &nbsp;·&nbsp;
+            <Link to="/site/status" style={{ color: 'var(--accent)', textDecoration: 'none' }}>
+              Shard Status
+            </Link>
+            &nbsp;·&nbsp;
+            <Link to="/admin/login" style={{ color: '#5d6b7d', textDecoration: 'none' }}>
+              Admin
+            </Link>
+          </span>
+        </div>
       </div>
     </footer>
   )

client/src/styles/theme.css

@@ -1009,6 +1009,47 @@ button[disabled] {
   border-color: #8a4b47;
 }
 
+/* Site footer: powered-by badge left-justified, info centered. */
+.site-footer-inner {
+  position: relative;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: 16px;
+  max-width: 1100px;
+  margin: 0 auto;
+}
+.site-footer-badge {
+  height: 56px;
+  width: auto;
+  flex: 0 0 auto;
+  opacity: 0.85;
+}
+.site-footer-info {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 6px;
+  text-align: center;
+}
+/* Pin the badge to the left while the info column stays visually centered. */
+@media (min-width: 641px) {
+  .site-footer-badge {
+    position: absolute;
+    left: 0;
+    top: 50%;
+    transform: translateY(-50%);
+  }
+}
+@media (max-width: 640px) {
+  .site-footer-inner {
+    flex-direction: column;
+  }
+  .site-footer-badge {
+    height: 44px;
+  }
+}
+
 /* Draft-preview banner on the public renderer. */
 .page-preview-banner {
   border: 1px solid var(--accent);