fix logout function, prepare for multi-account support

src/app/auth/import/step-1.tsx

@@ -79,7 +79,7 @@ export function ImportStep1Screen() {
 
   useEffect(() => {
     // save current step, if user close app and reopen it
-    setStep('/auth/import/step-1');
+    setStep('/auth/import');
   }, []);
 
   return (

src/app/auth/import/step-2.tsx

@@ -63,7 +63,7 @@ export function ImportStep2Screen() {
       const dir = await appConfigDir();
       const stronghold = await Stronghold.load(`${dir}/lume.stronghold`, data.password);
 
-      db.secureDB = stronghold;
+      if (!db.secureDB) db.secureDB = stronghold;
 
       // save privkey to secure storage
       await db.secureSave(pubkey, privkey);