## Summary
- Load the previous budget period (with transactions) in
`BudgetController::show()` and pass it to the frontend
- Overlay previous period's cumulative spending as a dashed line on the
budget spending chart
- Use day-of-period alignment (Day 1, Day 2...) when comparing so
periods of different lengths align
- Tooltip shows both "Spent" (current) and "Last period" values when
hovering
- Chart now shows the full period timeline (not just up to today)
- When no previous period exists, chart behavior is unchanged
## Screenshots
### Light mode
### Dark mode
## Test plan
- [x] Tests pass: `php artisan test --compact
tests/Feature/BudgetTest.php` (9 tests)
- [x] Pint formatting passes
- [x] ESLint + Prettier pass
- [ ] Manual: view a budget with a prior period — dashed line appears
- [ ] Manual: view a budget with no prior period — chart unchanged
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