Four-week tracked-hours calendar on Reports

Add a calendar to the top of the Reports page that shows the past four weeks day by day, so I can see which days we tracked time and how much. It's done when: - [ ] Four rows of seven days, Monday to Sunday, ending with this week - [ ] Each day shows its hours - [ ] Busier days are shaded darker - [ ] Today is outlined - [ ] It matches the attached sketch Leave the other reports and the week controls as they are, and don't add any libraries.

Past four weeks calendar added to Reports per sketch (Mon–Sun grid, hours, 4-step shading, today outlined); full gate + CI green; review fixes applied; visual check at 320–1280px light/dark passed. PR #53 merged.