Adds Kasse (Cash Register) module and related components

Introduces comprehensive cash management functionality with multiple view components for tracking daily transactions, filtering, and reconciliation

Implements:
- Cash calculation and difference tracking
- Dynamic tab switching
- Checkbox selection and row expansion
- Date filtering and approval mechanisms

CLAUDE.md

@@ -126,6 +126,50 @@ The solution follows a clean architecture pattern with these main projects:
 - `global.json` - .NET SDK version configuration (currently .NET 9.0)
 
 
+## CSS Guidelines
+
+### Grid + Subgrid for Table-like Layouts
+
+**ALWAYS** use CSS Grid with subgrid for table-like layouts (lists, data tables, card grids with aligned columns). This ensures columns align correctly across header, body, and rows.
+
+**Pattern:**
+```css
+/* Parent container defines the grid columns */
+swp-my-table {
+  display: grid;
+  grid-template-columns: 40px 1fr 100px 80px;  /* Define columns here */
+}
+
+/* Intermediate containers span all columns and use subgrid */
+swp-my-table-header,
+swp-my-table-body {
+  display: grid;
+  grid-column: 1 / -1;
+  grid-template-columns: subgrid;
+}
+
+/* Row items span all columns and use subgrid */
+swp-my-table-row {
+  display: grid;
+  grid-column: 1 / -1;
+  grid-template-columns: subgrid;
+  align-items: center;
+}
+```
+
+**Key principles:**
+1. Column definitions go on the **parent container only**
+2. All children use `grid-column: 1 / -1` to span all columns
+3. All children use `grid-template-columns: subgrid` to inherit columns
+4. Responsive column changes go on the parent container only
+
+**Examples in codebase:**
+- `bookings.css` - swp-booking-list / swp-booking-item
+- `notifications.css` - swp-notification-list / swp-notification-item
+- `attentions.css` - swp-attention-list / swp-attention-item
+- `kasse.css` - swp-kasse-table / swp-kasse-table-row
+
+
 ## NEVER Lie or Fabricate
 
 <CRITICAL> NEVER lie or fabricate. Violating this = immediate critical failure.