Add stats, profiles, avatars and palaute

Step 6. The surfaces around the review loop.

- Nine leaderboards, ordered and limited in SQL, each with a deterministic
  tie-break so a tied board doesn't reshuffle between reloads. Min 3 reviews
  to qualify, for reviewer boards too
- Profiles show counts and history-wide averages and the member's songs,
  never a list of their reviews — per-song opinion stays gated
- Avatars: 5MB in, 256px JPEG out, ffmpeg's re-encode being the validation.
  No upload still means initials, and avatars are public
- Changing your own password requires the current one and drops your other
  sessions
- Palaute: free text plus the page you were on, carried in a footer link, and
  the user agent from the header. Reporters see their own; the admin resolves
  them with a timestamp rather than a status enum
- Admin gained the song list with delete, the reports page, and an open-report
  count on the dashboard

Two theme fixes the screenshots caught: leaderboard ranks need a CSS counter
because display:grid suppresses list markers, and count-based boards were
printing 3.0 where they mean 3.

render.go

@@ -17,6 +17,16 @@ var assetFS embed.FS
 var funcs = template.FuncMap{
 	"fidate": func(t time.Time) string { return t.Local().Format("2.1.2006 15:04") },
 	"score":  func(f *float64) string { return strconv.FormatFloat(*f, 'f', 1, 64) },
+	"value":  func(f float64) string { return strconv.FormatFloat(f, 'f', 1, 64) },
+	// Lets one board partial be called with a title and a list, instead of two near-identical
+	// partials per leaderboard.
+	"dict": func(pairs ...any) map[string]any {
+		m := map[string]any{}
+		for i := 0; i+1 < len(pairs); i += 2 {
+			m[pairs[i].(string)] = pairs[i+1]
+		}
+		return m
+	},
 }
 
 // Each page is parsed with the layout into its own set, so two pages may both define "content".