Add timeline view, right-click context menu, and fix Express trust proxy

- backend/server.js: Add app.set('trust proxy', 1) to fix express-rate-limit
  ValidationError when app runs behind nginx reverse proxy
- ScheduleView.jsx: Add right-click context menu on reservation blocks with
  Edit and Delete options; closes on click-outside or Escape
- ScheduleView.module.css: Add context menu styles
- TimelineView.jsx: New Gantt-style monthly timeline view showing all
  reservations sorted by date, with month navigation and right-click menu
- TimelineView.module.css: Styles for the timeline view
- App.jsx: Add 'タイムライン' tab to navigation

Co-authored-by: pdf114514 <57948770+pdf114514@users.noreply.github.com>
Agent-Logs-Url: https://github.com/pdf114514/CarReservation/sessions/d03ca12c-21ce-45a0-881f-919d6635e7fb

frontend/src/components/ScheduleView.jsx

@@ -58,6 +58,10 @@ export default function ScheduleView() {
   const [modal, setModal] = useState(null);
   // null | { mode: 'create', prefill: {...} } | { mode: 'edit', reservation: {...} }
 
+  // Context menu state (right-click on reservation)
+  const [contextMenu, setContextMenu] = useState(null);
+  // null | { x, y, reservation }
+
   const gridRef = useRef(null);
   const movingRef = useRef(null); // keeps latest moving state for event handlers
 
@@ -238,6 +242,19 @@ export default function ScheduleView() {
     };
   }, [handleGridMouseMove, handleGridMouseUp]);
 
+  // Close context menu on any click or Escape
+  useEffect(() => {
+    if (!contextMenu) return;
+    const close = () => setContextMenu(null);
+    const onKey = (e) => { if (e.key === 'Escape') close(); };
+    window.addEventListener('click', close);
+    window.addEventListener('keydown', onKey);
+    return () => {
+      window.removeEventListener('click', close);
+      window.removeEventListener('keydown', onKey);
+    };
+  }, [contextMenu]);
+
   // --- Reservation drag to move ---
   const handleReservationMouseDown = (e, reservation) => {
     e.stopPropagation();
@@ -508,6 +525,11 @@ export default function ScheduleView() {
                             setModal({ mode: 'edit', reservation: r });
                           }
                         }}
+                        onContextMenu={(e) => {
+                          e.preventDefault();
+                          e.stopPropagation();
+                          setContextMenu({ x: e.clientX, y: e.clientY, reservation: r });
+                        }}
                         title={`${r.customer_name || '予約'}\n${r.start_date} 〜 ${r.end_date}${r.notes ? '\n' + r.notes : ''}`}
                       >
                         <span className={styles.blockText}>
@@ -544,6 +566,34 @@ export default function ScheduleView() {
           onClose={() => setModal(null)}
         />
       )}
+
+      {/* Right-click context menu */}
+      {contextMenu && (
+        <div
+          className={styles.contextMenu}
+          style={{ left: contextMenu.x, top: contextMenu.y }}
+          onClick={(e) => e.stopPropagation()}
+        >
+          <button
+            className={styles.contextMenuItem}
+            onClick={() => {
+              setModal({ mode: 'edit', reservation: contextMenu.reservation });
+              setContextMenu(null);
+            }}
+          >
+            ✏️ 編集
+          </button>
+          <button
+            className={`${styles.contextMenuItem} ${styles.contextMenuItemDelete}`}
+            onClick={async () => {
+              setContextMenu(null);
+              await handleModalDelete(contextMenu.reservation.id);
+            }}
+          >
+            🗑️ 削除
+          </button>
+        </div>
+      )}
     </div>
   );
 }