Apply the theme: tokens, Oswald, song cards, toasts

The theme handoff encoded as CSS custom properties rather than a Tailwind
config, since there is no Tailwind here. Palette, spacing, radii, shadows and
motion follow it as written; docs/theme.md lists what differs and why.

- Oswald vendored as a 21KB variable woff2, latin subset, no CDN. Its phantom
  weight 900 resolved to 700 — loading a weight you don't have is what made
  the brand render differently per platform
- color-scheme: dark makes the native audio element fit the palette, which
  was the handoff's complaint about it
- Songs are text cards rather than artwork tiles, because there is no
  artwork. The unreviewed state keeps its red-brown border and gains a badge,
  so it is never carried by colour alone
- Nav is the three-column grid; the mobile menu is <details>, no JS
- Flash messages became bottom-right toasts

Favicon carried over from the Nuxt project.

templates/partials/player.html

@@ -2,21 +2,21 @@
 <audio controls preload="none" src="/audio/{{.ID}}" class="player"></audio>
 {{end}}
 
-{{define "songrow"}}
-<tr>
-  <td>
-    <a href="/songs/{{.ID}}">{{.Title}}</a>
-    <span class="muted"> — {{.Artist}}</span>
-    {{if .Own}}<span class="tag">oma</span>{{else if .Reviewed}}<span class="tag done">arvosteltu</span>{{end}}
-  </td>
-  <td class="nowrap">{{.GenreLabel}}</td>
-  <td class="nowrap">{{.Length}}</td>
-  <td class="nowrap">
-    {{if .Average}}<strong>{{score .Average}}</strong> <span class="muted">({{.ReviewCount}})</span>
-    {{else if .ReviewCount}}<span class="muted">{{.ReviewCount}} arvostelua</span>
-    {{else}}<span class="muted">—</span>{{end}}
-  </td>
-</tr>
+{{define "songcard"}}
+<a class="songcard{{if and (not .Own) (not .Reviewed)}} unreviewed{{end}}" href="/songs/{{.ID}}">
+  {{with .Average}}<span class="scorebadge">{{score .}}</span>{{end}}
+  <span class="title">{{.Title}}</span>
+  <span class="artist">{{.Artist}}</span>
+  <span class="meta">
+    <span class="badge genre">{{.GenreLabel}}</span>
+    <span>{{.Length}}</span>
+    <span>{{.Submitter}}</span>
+    {{if .Own}}<span class="badge admin">oma</span>
+    {{else if .Reviewed}}<span class="badge reviewed">arvosteltu</span>
+    {{else}}<span class="badge pending">arvostelematta</span>{{end}}
+    {{if .ReviewCount}}<span>{{.ReviewCount}} arvostelua</span>{{end}}
+  </span>
+</a>
 {{end}}
 
 {{define "scorefield"}}
@@ -27,4 +27,7 @@
     <output>{{.}}</output>
   </span>
 </label>
+<span class="scorescale" aria-hidden="true">
+  <span>1</span><span>25</span><span>50</span><span>75</span><span>100</span>
+</span>
 {{end}}