refactor: clean up unused catch variables

frontend/src/components/editor/ComposeCanvas.tsx

@@ -122,7 +122,7 @@ export function ComposeCanvas({
   // re-calculates height based on content and applies the zoom transform
   const syncViewport = useCallback(() => {
     if (!(fabricRef.current && wrapperRef.current)) return;
-    textboxRef.current.initDimensions();
+    textboxRef.current?.initDimensions();
 
     const minHeight = initialData?.canvasHeight ?? DEFAULT_LOGICAL_HEIGHT;
     logicalSizeRef.current.height = measureLogicalContentHeight(

frontend/src/components/editor/PostSealModal.tsx

@@ -63,7 +63,11 @@ export function PostSealModal({
               type="button"
               data-testid="view-letter-btn"
               className="btn btn-primary btn-sm"
-              onClick={() => navigate(PATHS.read(sealedTargetId!))}
+              onClick={() => {
+                if (sealedTargetId) {
+                  navigate(PATHS.read(sealedTargetId));
+                }
+              }}
             >
               View letter
             </button>

frontend/src/hooks/useAuth.ts

@@ -32,7 +32,7 @@ export const useAuth = () => {
   const logout = async () => {
     try {
       await api.post(endpoints.LOGOUT);
-    } catch (_error) {
+    } catch {
     } finally {
       clearAuth();
       setMasterKey(null);

frontend/src/pages/Activate.tsx

@@ -26,7 +26,7 @@ export default function Activate() {
                 });
                 await publicApi.get(url);
                 setStatus("success");
-      } catch (_err) {
+            } catch {
                 setStatus("error");
             }
         };