Improves header drawer layout and drag behavior

Implements dynamic item positioning and layout recalculation for header drawer

- Adds ISO date tracking for header items
- Introduces dynamic row allocation algorithm
- Updates drawer expansion logic during drag operations
- Calculates and adjusts drawer height based on item tracks

wwwroot/css/v2/calendar-v2-layout.css

@@ -77,9 +77,6 @@ swp-header-drawer {
   grid-template-columns: subgrid;
   grid-column: 1 / -1;
   grid-row: 2;
-  grid-auto-rows: 28px;
-  gap: 2px 0;
-  height: 0;
   overflow: hidden;
   background: var(--color-background-alt);
   border-bottom: 1px solid var(--color-border);