fix: handle type errors in build

frontend/src/pages/Drawer.tsx

@@ -175,7 +175,7 @@ export default function Drawer() {
                   id={letter.public_id}
                   preview={letter.metadata?.recipient || "Future Self"}
                   timestamp={formatRelativeDate(letter.updated_at)}
-                  unlock_at={formateRelativeDateWithoutTime(letter.unlock_at)}
+                  unlock_at={formateRelativeDateWithoutTime(letter.unlock_at || "")}
                   isLocked={letter.unlock_at > new Date().toISOString()}
                 />
               ))}

frontend/src/pages/Reader.test.tsx

@@ -69,7 +69,7 @@ describe("Reader Page", () => {
       }),
     );
 
-    const {container} = render(
+    render(
       <MemoryRouter initialEntries={[`/read/${mockPublicId}#${sharingKey}`]}>
         <Routes>
           <Route path="/read/:public_id" element={<Reader />} />