fix: link dashboard artist names to detail pages

Task 8's ignore/restore/ignore-singles actions live on the artist detail
page, but the dashboard rendered artist names as plain text with no link,
making those actions unreachable through normal UI navigation. Wrap the
name in an anchor to /artist/{id} and assert the link in the dashboard test.

internal/web/templates/dashboard.html

@@ -33,7 +33,7 @@
         <tbody>
             {{ range .Artists }}
             <tr>
-                <td>{{ .Name }}</td>
+                <td><a href="/artist/{{ .ID }}">{{ .Name }}</a></td>
                 <td class="count {{ if eq .MissingCount 0 }}count-zero{{ else }}count-missing{{ end }}">
                     {{ .MissingCount }}
                 </td>