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.

stats_test.go

@@ -0,0 +1,120 @@
+package main
+
+import (
+	"context"
+	"testing"
+)
+
+// A song qualifies only at minReviews, and the order is decided in SQL — with a tie-break, so the
+// same ten come back in the same order every time.
+func TestLeaderboardThresholdAndOrder(t *testing.T) {
+	a := testApp(t)
+	ctx := context.Background()
+	submitter := a.seedMember(t, "[email protected]")
+	var reviewers []int64
+	for _, e := range []string{"[email protected]", "[email protected]", "[email protected]"} {
+		reviewers = append(reviewers, a.seedMember(t, e))
+	}
+
+	loved := a.seedSong(t, submitter, "Rakastettu")
+	hated := a.seedSong(t, submitter, "Vihattu")
+	ignored := a.seedSong(t, submitter, "Kahdesti arvosteltu")
+
+	for _, r := range reviewers {
+		a.seedReview(t, loved, r, 90)
+		a.seedReview(t, hated, r, 20)
+	}
+	// One short of the threshold.
+	a.seedReview(t, ignored, reviewers[0], 100)
+	a.seedReview(t, ignored, reviewers[1], 100)
+
+	top, err := a.songLeaderboard(ctx, "avg(r.score)", "desc")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(top) != 2 {
+		t.Fatalf("top has %d entries, want 2 — the third song is below %d reviews", len(top), minReviews)
+	}
+	if top[0].ID != loved || top[1].ID != hated {
+		t.Fatalf("top order is %d, %d — want %d first", top[0].ID, top[1].ID, loved)
+	}
+	if top[0].Value != 90 || top[0].ReviewCount != 3 {
+		t.Fatalf("top entry = %v with %d reviews, want 90 and 3", top[0].Value, top[0].ReviewCount)
+	}
+
+	bottom, err := a.songLeaderboard(ctx, "avg(r.score)", "asc")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if bottom[0].ID != hated {
+		t.Fatalf("bottom starts with %d, want %d", bottom[0].ID, hated)
+	}
+
+	// Identical scores everywhere means stddev 0, so unified beats divisive on the same data.
+	unified, err := a.songLeaderboard(ctx, "stddev_pop(r.score)", "asc")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if unified[0].Value != 0 {
+		t.Fatalf("most unified has stddev %v, want 0", unified[0].Value)
+	}
+
+	// Ties are the common case in a ten-person club: the same query must return the same order.
+	first, _ := a.songLeaderboard(ctx, "count(r.id)", "desc")
+	second, _ := a.songLeaderboard(ctx, "count(r.id)", "desc")
+	for i := range first {
+		if first[i].ID != second[i].ID {
+			t.Fatal("a tied leaderboard reshuffles between calls — the tie-break is missing")
+		}
+	}
+}
+
+// Profiles are counts and history-wide averages. They never carry per-song opinions.
+func TestProfileStats(t *testing.T) {
+	a := testApp(t)
+	ctx := context.Background()
+	aino := a.seedMember(t, "[email protected]")
+	bertta := a.seedMember(t, "[email protected]")
+
+	song := a.seedSong(t, aino, "Testikappale")
+	a.seedReview(t, song, bertta, 80)
+	other := a.seedSong(t, bertta, "Berttan kappale")
+	a.seedReview(t, other, aino, 40)
+
+	p, err := a.profile(ctx, bertta, aino)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if p.Stats.SongsSubmitted != 1 || p.Stats.ReviewsWritten != 1 {
+		t.Fatalf("counts = %d songs, %d reviews; want 1 and 1",
+			p.Stats.SongsSubmitted, p.Stats.ReviewsWritten)
+	}
+	if p.Stats.AverageGiven == nil || *p.Stats.AverageGiven != 40 {
+		t.Fatalf("average given = %v, want 40", p.Stats.AverageGiven)
+	}
+	if p.Stats.AverageReceived == nil || *p.Stats.AverageReceived != 80 {
+		t.Fatalf("average received = %v, want 80", p.Stats.AverageReceived)
+	}
+	// Viewing someone else's profile does not expose their email.
+	if p.Email != "" {
+		t.Fatalf("another member's email leaked: %q", p.Email)
+	}
+	// Their songs still obey the viewer's own reveal rule. Bertta reviewed this one, so she sees
+	// its average here.
+	if len(p.Songs) != 1 {
+		t.Fatalf("profile lists %d songs, want 1", len(p.Songs))
+	}
+	if p.Songs[0].Average == nil {
+		t.Fatal("a reviewer cannot see the average of a song they reviewed")
+	}
+
+	// A third member who has reviewed nothing must not learn it from the profile page.
+	cecilia := a.seedMember(t, "[email protected]")
+	p, err = a.profile(ctx, cecilia, aino)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if p.Songs[0].Average != nil {
+		t.Fatal("profile leaked a song average to someone who has not reviewed it")
+	}
+}