Update progress and implement UI/UX refinements post-checkout phase

- Updated last modified date and overall progress in project documentation.
- Implemented critical UX improvements including route localization to English, cart item position stability, text selection prevention, and scrollbar styling fixes.
- Enhanced cart functionality with a new MockPayPalButton component and ensured cart state synchronization after order completion.
- Fixed accessibility issues with the cart edit button and improved responsive rendering for cart components.

These changes aim to enhance user experience and maintain consistency across the application.

tasks/00-PROGRESS.md

@@ -2,9 +2,9 @@
 
 ## my.experimenta.science
 
-**Last Updated:** 2025-01-03
+**Last Updated:** 2025-11-03
 **Overall Progress:** 73/144 tasks (50.7%)
-**Current Phase:** ✅ Phase 5 - Checkout (Complete)
+**Current Phase:** ✅ Phase 5 - Checkout (Complete) + UI/UX Refinements
 
 ---
 
@@ -30,11 +30,84 @@
 
 ## 🚀 Current Work
 
+**Recent: UI/UX Refinements (2025-11-03)**
+
+After completing Phase 5 (Checkout), we implemented critical UX improvements based on user testing:
+
+### Route Localization (English URLs):
+✅ **Comprehensive route migration from German to English**
+- `/kasse` → `/checkout` (checkout page)
+- `/zahlung` → `/payment` (payment page)
+- `/warenkorb` → `/cart` (cart - not a page, but reference updated)
+- `/bestellung/bestaetigen/[orderId]` → `/order/confirm/[orderId]` (order confirmation)
+- `/bestellung/erfolg/[orderId]` → `/order/success/[orderId]` (success page)
+- Updated all navigateTo() calls and NuxtLink references (11+ locations)
+- Files renamed: 4 page files, maintaining folder structure
+- **Rationale:** URLs should be English for international audience (CLAUDE.md updated)
+
+### Cart Sidebar Access Fix:
+✅ **Fixed "Warenkorb bearbeiten" button on checkout page**
+- Problem: Button linked to `/cart` page (doesn't exist - cart is sidebar/sheet)
+- Solution: Added CartSidebar/CartSheet to app.vue globally
+- Changed NuxtLink to button with `@click="openCart"` using useCartUI composable
+- Responsive rendering: CartSheet (mobile) / CartSidebar (desktop)
+- Tested with Playwright - cart sidebar now opens correctly
+
+### Cart Item Position Stability:
+✅ **Fixed items jumping positions during quantity updates**
+- Problem: Items swapped positions when updating quantity (PostgreSQL unpredictable order)
+- Root Cause: Database query had no ORDER BY clause in `server/utils/cart-helpers.ts`
+- Solution: Added `orderBy: asc(cartItems.addedAt)` to maintain chronological order
+- Impact: Items now maintain stable positions, preventing accidental wrong-item clicks
+
+### Text Selection Prevention:
+✅ **Prevented accidental text selection during fast clicking**
+- Problem: Double-clicking Plus/Minus buttons selected quantity numbers
+- Solution: Added `select-none` CSS class to:
+  - Quantity controls container
+  - Plus/Minus buttons
+  - Quantity display
+  - Subtotal section
+- Result: No text selection possible in cart item controls
+
+### Scrollbar Styling Fix:
+✅ **Fixed elliptical scrollbar appearance**
+- Problem: Scrollbar had excessive border-radius (`rounded-full`) looking like ellipse
+- Solution: Changed to `rounded-md` in `app/components/ui/scroll-area/ScrollBar.vue`
+- Result: Professional-looking scrollbar with appropriate 6px border-radius
+
+### Cart State Synchronization:
+✅ **Cart clears after order completion**
+- Backend already cleared cart in `/api/orders/confirm/[id].post.ts`
+- Added `fetchCart()` call in success page to sync frontend state
+- Result: Cart badge shows "0" after successful order
+
+### Mock PayPal Button Created:
+✅ **Created missing MockPayPalButton.vue component**
+- PayPal branding with official blue (#0070ba) and logo
+- 2-second mock payment simulation with loading state
+- Amount display with German currency formatting
+- Developer notice that it's a mock
+- Proper event emission for success callback
+
+**Files Modified (7):**
+1. `app/pages/checkout.vue` - Cart edit button + route updates
+2. `app/pages/payment.vue` - Route updates
+3. `app/pages/order/confirm/[orderId].vue` - Route updates
+4. `app/pages/order/success/[orderId].vue` - Cart refresh + route updates
+5. `app/components/MockPayPalButton.vue` - Created new component
+6. `app/components/Cart/CartItem.vue` - Text selection prevention
+7. `app/components/ui/scroll-area/ScrollBar.vue` - Border-radius fix
+8. `server/utils/cart-helpers.ts` - Stable ordering
+9. `app/app.vue` - Global cart components
+
+---
+
 **Phase 5: Checkout - COMPLETED ✅ (2025-01-03)**
 
 **Implementation Method:** Parallel agent-based development (4 agents) + comprehensive testing (4 test agents)
 
-**Completed in this session:**
+**Completed in previous session:**
 
 ### Implementation Phase (Agents 1-4):
 1. ✅ **Schema & API Endpoints** (Agent 1)
@@ -50,10 +123,10 @@
    - MockPayPalButton (simulates payment flow)
 
 3. ✅ **Pages** (Agent 3)
-   - `/kasse` - Checkout page with billing form
+   - `/kasse` - Checkout page with billing form (now `/checkout`)
-   - `/zahlung` - Mock PayPal payment page
+   - `/zahlung` - Mock PayPal payment page (now `/payment`)
-   - `/bestellung/bestaetigen/[orderId]` - Order confirmation
+   - `/bestellung/bestaetigen/[orderId]` - Order confirmation (now `/order/confirm/[orderId]`)
-   - `/bestellung/erfolg/[orderId]` - Success page
+   - `/bestellung/erfolg/[orderId]` - Success page (now `/order/success/[orderId]`)
 
 4. ✅ **Validation & Utilities** (Agent 4)
    - German error messages (277 lines)
@@ -559,6 +632,7 @@ Tasks:
 | 2025-11-03 | 37.2%            | Phase 4 - Cart       | ✅ Cart completed: 4 API endpoints, useCart composable, CartItem & CartSummary components, responsive UI (desktop sidebar + mobile FAB), 30-day persistence, full CRUD operations tested  |
 | 2025-01-03 | 37.2%            | Cart Refinement      | ✅ Cart UI fixes: Button hover-bug (relative positioning), CartItem layout (justify-between), quantity display, button styling (badge, spacing, border-radius, height). Educator page created. |
 | 2025-01-03 | 50.7%            | Phase 5 - Checkout   | ✅ Checkout completed: 18 files created (4 endpoints, 4 components, 4 pages, utilities), tested with 4 agents, 7 known issues documented for post-MVP                                     |
+| 2025-11-03 | 50.7%            | UX Refinements       | ✅ Route localization (DE→EN), cart item position stability (ordering), text selection prevention (select-none), scrollbar styling, cart state sync, MockPayPalButton creation, cart edit button fix |
 
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