chore: remove dead code orphaned by topbar redesign (#4)

The new topbar's "Refresh all" button replaces the old SSE-driven
"Load All" link and progress UI. With those gone, several pieces of
infrastructure had no callers left:

- GET /api/load-all-players, POST /api/populate-database, and
  GET /api/database-status — SSE endpoints with no frontend consumers
- #progress-section / #loading divs in players + courses pages
- .progress-container / .progress-bar / .progress-text / .loading CSS
- public/js/progress.js script (defines fetchRatingsWithProgress, never
  called, and loadAllPlayers, no longer wired) — to be deleted manually
  since the sandbox blocks rm

public/css/players.css

@@ -12,37 +12,6 @@
     background: #059669;
 }
 
-/* ── Progress ─────────────────────────────────── */
-
-.progress-container {
-    width: 100%;
-    background: var(--surface-3);
-    border-radius: var(--radius-xl);
-    padding: 3px;
-    margin: 20px 0;
-    overflow: hidden;
-}
-
-.progress-bar {
-    width: 0%;
-    height: 26px;
-    background: linear-gradient(135deg, var(--accent), var(--accent-hover));
-    border-radius: var(--radius-xl);
-    text-align: center;
-    line-height: 26px;
-    color: white;
-    font-weight: 600;
-    font-size: 12px;
-    transition: width 0.4s ease;
-}
-
-.progress-text {
-    text-align: center;
-    margin: 8px 0;
-    font-size: 13px;
-    color: var(--text-secondary);
-}
-
 /* ── Mobile helpers ───────────────────────────── */
 
 .mobile-only {