feat: section aide rapide dans le dashboard stats

- Boite elegante sous les statistiques avec icone clavier
- 10 raccourcis clavier essentiels (palette, recherche, edition)
- Badges style touches clavier (mono, accent, bordure)
- Astuce Ctrl+survol et editeur Forge
- Toggle masquer/afficher avec persistence localStorage
- Layout grid responsive (auto-fill minmax 260px)

frontend/style.css

@@ -6446,6 +6446,88 @@ body.popup-mode .content-area {
 }
 .conflict-btn:hover { background: var(--bg-hover); }
 
+/* ── Quick Help (Dashboard) ── */
+.quick-help {
+  margin-top: 16px;
+  background: var(--bg-card, var(--bg-secondary));
+  border: 1px solid var(--border);
+  border-radius: var(--radius-lg);
+  overflow: hidden;
+}
+.qh-header {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  padding: 10px 14px;
+  font-size: 0.8rem;
+  font-weight: 600;
+  color: var(--text-secondary);
+  border-bottom: 1px solid var(--border);
+  user-select: none;
+}
+.qh-header i { color: var(--accent); opacity: 0.7; }
+.qh-toggle {
+  margin-left: auto;
+  background: none;
+  border: none;
+  color: var(--text-muted);
+  cursor: pointer;
+  font-size: 1rem;
+  line-height: 1;
+  padding: 2px 6px;
+  border-radius: 4px;
+}
+.qh-toggle:hover { color: var(--text-secondary); background: var(--bg-hover); }
+.qh-body {
+  padding: 10px 14px 14px;
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
+  gap: 6px 20px;
+}
+.qh-body.collapsed { display: none; }
+.qh-row {
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  padding: 4px 0;
+}
+.qh-kbd {
+  display: inline-flex;
+  align-items: center;
+  padding: 2px 8px;
+  font-family: var(--mono);
+  font-size: 0.7rem;
+  font-weight: 500;
+  color: var(--accent-text, #79c0ff);
+  background: var(--accent-bg, #1f2a3a);
+  border: 1px solid var(--border-md, #30363d);
+  border-radius: 4px;
+  white-space: nowrap;
+  min-width: 0;
+  letter-spacing: 0.3px;
+}
+.qh-desc {
+  font-size: 0.78rem;
+  color: var(--text-secondary);
+}
+.qh-divider {
+  grid-column: 1 / -1;
+  height: 1px;
+  background: var(--border);
+  margin: 6px 0 8px;
+}
+.qh-tip {
+  grid-column: 1 / -1;
+  display: flex;
+  align-items: flex-start;
+  gap: 8px;
+  font-size: 0.75rem;
+  color: var(--text-muted);
+  line-height: 1.5;
+}
+.qh-tip i { color: var(--warn); flex-shrink: 0; margin-top: 1px; }
+.qh-tip strong { color: var(--text-secondary); }
+
 /* ── Webhooks UI ── */
 .webhook-item {
   display: flex;