feat: admin panel - Settings, Categories, Payment Wallets, Seed/Clear data, User Balances

- Settings page: bot token (masked), admin IDs, commission config, WireGuard status
- Categories page: CRUD with product count, delete guard
- Payment Wallets page: commission wallets display, toggle, percentage
- Users page: balance adjustment form (total_balance / bonus_balance) with audit log
- Seed & Reset page: seed demo data (5 users, 10 products, 5 wallets, 5 purchases)
  and clear all data button with confirmation
- Dashboard: flash messages for seed/clear success
- Fixed seed.js: use dynamic IDs instead of hardcoded to avoid FK violations
- Fixed seed.js: clear all tables before seeding to avoid UNIQUE constraints

src/admin/public/style.css

@@ -206,6 +206,30 @@ textarea { min-height: 80px; resize: vertical; }
 code { background: #f1f5f9; padding: 0.1rem 0.3rem; border-radius: 3px; font-size: 0.85em; }
 pre { font-size: 0.8rem; white-space: pre-wrap; word-break: break-all; max-width: 300px; }
 
+.muted { color: var(--muted); font-size: 0.85rem; }
+
+.settings-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
+  gap: 1rem;
+}
+
+.seed-card {
+  background: var(--card);
+  border: 1px solid var(--border);
+  border-radius: var(--radius);
+  padding: 1.5rem;
+  margin-bottom: 1rem;
+}
+
+.seed-card.danger {
+  border-color: var(--danger);
+  border-width: 2px;
+}
+
+.seed-card h2 { margin-bottom: 0.5rem; }
+.seed-card p { margin-bottom: 1rem; color: var(--muted); }
+
 @media (max-width: 640px) {
   .topnav { flex-direction: column; align-items: flex-start; }
   .logout-btn { margin-left: 0; }