fix: skip checkAuth on route change when already authenticated

app/[locale]/calendar/page.tsx

@@ -126,8 +126,15 @@ export default function CalendarPage() {
     }
   }, [events, detailEvent]);
 
-  // Check auth on mount
+  // Check auth on mount — skip when already authenticated so that navigating
+  // between routes doesn't retrigger checkAuth's transient `{ client: null,
+  // isLoading: true }` reset, which was flashing the spinner on every nav.
   useEffect(() => {
+    const state = useAuthStore.getState();
+    if (state.isAuthenticated && state.client) {
+      setInitialCheckDone(true);
+      return;
+    }
     checkAuth().finally(() => {
       setInitialCheckDone(true);
     });

app/[locale]/contacts/page.tsx

@@ -103,8 +103,15 @@ export default function ContactsPage() {
   const [isListResizing, setIsListResizing] = useState(false);
   const listDragStartWidth = useRef(384);
 
-  // Check auth on mount
+  // Check auth on mount — skip when already authenticated so that navigating
+  // between routes doesn't retrigger checkAuth's transient `{ client: null,
+  // isLoading: true }` reset, which was flashing the spinner on every nav.
   useEffect(() => {
+    const state = useAuthStore.getState();
+    if (state.isAuthenticated && state.client) {
+      setInitialCheckDone(true);
+      return;
+    }
     checkAuth().finally(() => {
       setInitialCheckDone(true);
     });

app/[locale]/files/page.tsx

@@ -105,8 +105,15 @@ export default function FilesPage() {
 
   const detailResource = detailName ? resources.find(r => r.name === detailName) || null : null;
 
-  // Check auth on mount
+  // Check auth on mount — skip when already authenticated so that navigating
+  // between routes doesn't retrigger checkAuth's transient `{ client: null,
+  // isLoading: true }` reset, which was flashing the spinner on every nav.
   useEffect(() => {
+    const state = useAuthStore.getState();
+    if (state.isAuthenticated && state.client) {
+      setInitialCheckDone(true);
+      return;
+    }
     checkAuth().finally(() => {
       setInitialCheckDone(true);
     });

app/[locale]/page.tsx

@@ -455,8 +455,15 @@ export default function Home() {
     document.title = title;
   }, [showComposer, composerMode, selectedEmail, selectedMailbox, mailboxes, t, appName]);
 
-  // Check auth on mount
+  // Check auth on mount — skip when already authenticated so that navigating
+  // between routes doesn't retrigger checkAuth's transient `{ client: null,
+  // isLoading: true }` reset, which was flashing the spinner on every nav.
   useEffect(() => {
+    const state = useAuthStore.getState();
+    if (state.isAuthenticated && state.client) {
+      setInitialCheckDone(true);
+      return;
+    }
     checkAuth().finally(() => {
       setInitialCheckDone(true);
     });

app/[locale]/settings/page.tsx

@@ -179,7 +179,15 @@ export default function SettingsPage() {
   const [isResizing, setIsResizing] = useState(false);
   const dragStartWidth = useRef(256);
 
+  // Check auth on mount — skip when already authenticated so that navigating
+  // between routes doesn't retrigger checkAuth's transient `{ client: null,
+  // isLoading: true }` reset, which was flashing the spinner on every nav.
   useEffect(() => {
+    const state = useAuthStore.getState();
+    if (state.isAuthenticated && state.client) {
+      setInitialCheckDone(true);
+      return;
+    }
     checkAuth().finally(() => {
       setInitialCheckDone(true);
     });