Hours tracked calendar for past four weeks

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.

Added a Past four weeks calendar to the top of Reports: 4 rows of Mon–Sun ending this week, each day's hours, 4 shade levels, today outlined, matching the sketch. Gate green, visual check done (desktop, mobile, dark). PR #86 queued to the lane. Memory: none applied.