feat: sticky calendar header and days (#568)

* feat: sticky calendar days

* feat: partial height borders for day labels

* feat: make calendar header actually sticky

* fix: remove unneeded gap

* refactor: add preston as co-author

Co-authored-by: Preston-Cook <preston.l.cook@gmail.com>

* fix: z-index issues with export sub-buttons

---------

Co-authored-by: Preston-Cook <preston.l.cook@gmail.com>
Co-authored-by: doprz <52579214+doprz@users.noreply.github.com>

src/views/components/calendar/CalendarGridCell.tsx

@@ -17,8 +17,8 @@ function CalendarCell({ row, col }: Props): JSX.Element {
         <div
             className='h-full w-full flex items-center border-b border-r border-gray-300'
             style={{
-                gridColumn: col + 3,
-                gridRow: `${2 * row + 2} / ${2 * row + 4}`,
+                gridColumn: col + 3, // start in the 3rd 1-index column
+                gridRow: `${2 * row + 3} / ${2 * row + 5}`, // Span 2 rows, skip 2 header rows
             }}
         >
             <div className='h-0 w-full border-t border-gray-300/25' />