fix: MEDIUM issues #23-#30 — stale deps, export modal, cache race, StrictMode dedup, SeatingService ref, SVG import persist, group-as-block multi-select, session expiry

frontend/src/services/api.ts

@@ -349,12 +349,20 @@ export async function createBlockTyped(token: string, drawingId: string, block:
   return dbBlockToFrontend(raw);
 }
 
-const projectLoadCache = new Map<string, Promise<ProjectData>>();
+const projectLoadCache = new Map<string, { promise: Promise<ProjectData>; requestId: number }>();
+const projectLoadRequestCounter = new Map<string, number>();
 
 export async function loadProjectDataTyped(token: string, projectId: string): Promise<ProjectData> {
-  // Dedup concurrent calls (React StrictMode double-render)
+  // Generate a new request ID to track the latest request for this project
+  const currentRequestId = (projectLoadRequestCounter.get(projectId) ?? 0) + 1;
+  projectLoadRequestCounter.set(projectId, currentRequestId);
+
+  // Dedup concurrent calls (React StrictMode double-render): if there is an in-flight
+  // request with the same ID, reuse it. Otherwise start a fresh one.
   const existing = projectLoadCache.get(projectId);
-  if (existing) return existing;
+  if (existing && existing.requestId === currentRequestId - 1) {
+    return existing.promise;
+  }
 
   const promise = (async () => {
     const drawings = await getDrawings(token, projectId);
@@ -373,6 +381,13 @@ export async function loadProjectDataTyped(token: string, projectId: string): Pr
       getBlocks(token, drawing.id),
     ]);
 
+    // Only use the result if this is still the latest request for this project
+    const latestRequestId = projectLoadRequestCounter.get(projectId);
+    if (latestRequestId !== currentRequestId) {
+      // A newer request superseded this one — reject to prevent stale data
+      throw new Error('Superseded by a newer load request');
+    }
+
     return {
       project,
       drawing,
@@ -382,8 +397,14 @@ export async function loadProjectDataTyped(token: string, projectId: string): Pr
     };
   })();
 
-  projectLoadCache.set(projectId, promise);
-  promise.finally(() => projectLoadCache.delete(projectId));
+  projectLoadCache.set(projectId, { promise, requestId: currentRequestId });
+  promise.finally(() => {
+    // Only clear cache if this is still the latest request
+    const cached = projectLoadCache.get(projectId);
+    if (cached && cached.requestId === currentRequestId) {
+      projectLoadCache.delete(projectId);
+    }
+  });
   return promise;
 }