**Patch Plan**
Centralize email normalization in the lookup function so all queries match the stored format, eliminating case/whitespace mismatches.

**Exact File/Function Edits**
`store.py` → `get_user`:
```python
def get_user(email):
    return USERS.get(email.strip().lower())
```

**Regression Test**
```python
def test_login_email_normalization():
    save_user(" Admin@Example.com ", "hash123")
    assert login("admin@example.com", "hash123") is True
```