### Patch Plan

**File:** `store.py`
**Function:** `get_user`
**Edit:** Update the lookup to normalize the input email to match the storage logic.
```python
def get_user(email):
    return USERS.get(email.strip().lower())
```

### Regression Test
**Scenario:** Login with a lowercase/trimmed email after registering with mixed-case/padded email.
1. Call `save_user("  User@Example.com  ", "hash123")`
2. Call `login("user@example.com", "hash123")`
3. **Expected Result:** `True` (Previously `False`)