feat(leaderboard): add global rankings screen with solo/multi/all filters

app/globals.css

@@ -1323,6 +1323,9 @@ body {
   position: absolute;
   top: 16px;
   right: 16px;
+  display: flex;
+  align-items: center;
+  gap: 8px;
 }
 
 .btn-account {
@@ -1545,3 +1548,128 @@ body {
 }
 .game-path-sep { margin: 0 2px; }
 .game-path-end { color: var(--green); font-weight: 600; }
+
+/* ================================
+   Leaderboard
+   ================================ */
+
+.leaderboard-screen {
+  max-width: 640px;
+  margin: 0 auto;
+  padding: 24px 16px 48px;
+}
+
+.leaderboard-header {
+  display: flex;
+  align-items: center;
+  gap: 16px;
+  margin-bottom: 24px;
+}
+
+.leaderboard-title {
+  font-size: 24px;
+  font-weight: 800;
+}
+
+.leaderboard-tabs {
+  display: flex;
+  gap: 8px;
+  margin-bottom: 20px;
+}
+
+.leaderboard-tab {
+  flex: 1;
+  padding: 8px;
+  border-radius: var(--radius);
+  border: 1px solid var(--border);
+  background: var(--bg-2);
+  color: var(--text-muted);
+  font-size: 13px;
+  font-weight: 600;
+  cursor: pointer;
+  transition: background var(--transition), color var(--transition);
+}
+
+.leaderboard-tab.active {
+  background: var(--accent);
+  color: #fff;
+  border-color: var(--accent);
+}
+
+.leaderboard-loading {
+  display: flex;
+  justify-content: center;
+  padding: 48px;
+}
+
+.leaderboard-empty {
+  text-align: center;
+  color: var(--text-muted);
+  padding: 48px 0;
+}
+
+.leaderboard-list {
+  display: flex;
+  flex-direction: column;
+  gap: 10px;
+}
+
+.leaderboard-row {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  padding: 14px 16px;
+  background: var(--bg-2);
+  border-radius: var(--radius);
+  border: 1px solid var(--border);
+}
+
+.leaderboard-row.top {
+  border-color: var(--accent);
+  background: color-mix(in srgb, var(--accent) 8%, var(--bg-2));
+}
+
+.lb-rank {
+  font-size: 22px;
+  width: 32px;
+  text-align: center;
+  flex-shrink: 0;
+}
+
+.lb-name {
+  font-weight: 700;
+  font-size: 15px;
+  flex: 1;
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.lb-stats {
+  display: flex;
+  gap: 16px;
+  flex-shrink: 0;
+}
+
+.lb-stat {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 1px;
+}
+
+.lb-stat-val {
+  font-size: 15px;
+  font-weight: 800;
+  font-variant-numeric: tabular-nums;
+  color: var(--text);
+}
+
+.lb-stat-label {
+  font-size: 9px;
+  font-weight: 700;
+  letter-spacing: 0.06em;
+  text-transform: uppercase;
+  color: var(--text-muted);
+}