Add the copyright line to the footer

No year: a bare mark never goes stale, and a hardcoded one quietly says
abandoned.

static/style.css

@@ -934,3 +934,6 @@ img.avatar { object-fit: cover; }
 .slogan { font-family: var(--font-display); letter-spacing: 0.02em; }
 .slogan.hero { color: var(--gold-2); font-size: 1.1rem; text-transform: uppercase;
                margin: calc(-1 * var(--space-2)) 0 var(--space-5); }
+
+.copyright { color: var(--muted); }
+.copyright::before { content: "·"; margin: 0 var(--space-2); }

templates/layout.html

@@ -64,6 +64,7 @@
       <a href="/report?from={{.Path}}">Ilmoita ongelmasta</a> ·
     {{end}}
     <span class="slogan">We know good music, baby!</span>
+    <span class="copyright">© Kessinen</span>
   </footer>
 
   {{with .Flash}}