### Patch Plan

**store.py**
Modify `get_user` to normalize the input email consistently with `save_user`.

```python
def get_user(email):
    return USERS.get(email.strip().lower())
```

**routes.py**
No changes required.

### Regression Test
**Scenario:** Login with whitespace and mixed casing.
**Input:** `login("  User@Example.com  ", "correct_hash")`
**Expected Result:** `True` (assuming the user was saved as `user@example.com`).