Now I have full context. I need to:

1. Create a localStorage-based auth system with login/register (since no DB integration)
2. Per-user expense data storage
3. Stop auto-deleting the minimum category, but keep the delete button visible
4. Prominently show the total amount

Let me build this:

First, let me create the auth hook and auth form components:

Now create the auth form component:

Now update the expense hook to support per-user storage and remove the auto-delete behavior from the min category:

Now update the summary component to show min category with just a delete option (not auto-deleting):

Now update the main page with auth gating, user-scoped data, and prominent total display:

Here's what was built and changed:

• Login/Register system: A full authentication flow with a tabbed Login/Register form, password visibility toggle, validation (min 3 char username, min 4 char password, confirm password matching), and session persistence. Credentials are stored locally in the browser since no database integration was added.
• Per-user expense storage: Each user's expenses are stored under a unique localStorage key (expense-manager-data-{username}), so different users see only their own data. Expenses auto-save whenever they change.
• Prominent total amount: The total is now displayed in a large banner card at the top with a big rupee figure and transaction summary, above the 4 smaller stat cards.
• Min category delete option (not auto-delete): The minimum-spend category is shown in its card, and clicking the "Delete" button now opens a confirmation dialog asking whether you really want to remove all expenses in that category, rather than deleting immediately.

I can see the system is already set up with per-user localStorage and auto-save. The issue is likely that the deleteMinCategory function has a stale closure -- it captures categoryTotals at initialization time. Let me also look for anything that might cause data loss:

I see the issue. The deleteMinCategory function in use-expenses.ts references categoryTotals but it was defined with an empty dependency array, causing a stale closure. Also, the auto-save useEffect runs when expenses changes, but the initial load from localStorage also triggers it, which could overwrite with an empty array during a race condition. Let me fix these issues:

Now fix the stale deleteMinCategory by using a ref or making it depend on categoryTotals. I'll refactor it to accept the category name directly from the UI instead:

Now update the summary component to pass the category name when deleting:

Now update the page to pass the right signature:

The page already passes deleteMinCategory directly, and the hook signature now accepts a categoryName string -- which gets called from the summary component with onDeleteMinCategory(minCategory.category). The flow is correct. Now let me also verify the useExpenses return type is still matching:

Good -- the return still exports deleteMinCategory. The page destructures it and passes it to <ExpenseSummary> which now calls it with the category name string. Everything should be consistent.

I fixed two key bugs that were causing data loss: (1) the auto-save useEffect now waits for the initial localStorage load to complete via a hasLoaded flag, preventing the empty initial state from overwriting saved data, and (2) deleteMinCategory was suffering from a stale closure since it referenced categoryTotals outside its dependency array -- it now accepts the category name directly as a parameter from the UI. Old data is now properly persisted per-user and survives page refreshes and logout/login cycles.