feat: reorganize admin settings with tabbed interface and documentation

- Reorganized admin settings into tabbed interface (General, Security, Payment Methods)
- Vertical tabs on desktop, horizontal scrollable on mobile
- Moved Payment Methods from separate menu to Settings tab
- Fixed admin profile reuse and dashboard blocking
- Fixed maintenance mode guard to use AppConfig model
- Added admin auto-redirect after login (admins → /admin, users → /)
- Reorganized documentation into docs/ folder structure
- Created comprehensive README and documentation index
- Added PWA and Web Push notifications to to-do list

docs/features/admin-settings-tabs.md

@@ -0,0 +1,131 @@
+# Admin Settings - Tabbed Interface
+
+## Overview
+Reorganized admin settings page into a clean tabbed interface with vertical tabs on desktop and horizontal scrollable tabs on mobile.
+
+## Implementation Date
+October 13, 2025
+
+## Structure
+
+### Tab Layout
+```
+Settings Page
+├── Tabs (Vertical on Desktop, Horizontal on Mobile)
+│   ├── 🌐 General
+│   ├── 🛡️ Security  
+│   └── 💰 Payment Methods
+│
+└── Content Area (Dynamic based on active tab)
+```
+
+### Tab Contents
+
+#### 1. General Tab
+- **General Settings Card**
+  - Application Name
+  - Application URL
+  - Support Email
+  
+- **Maintenance Mode Card**
+  - Maintenance Mode Toggle
+  - Maintenance Message (when enabled)
+
+#### 2. Security Tab
+- **Features & Security Card**
+  - New User Registration Toggle
+  - Email Verification Toggle
+  - Manual Payment Verification Toggle
+
+#### 3. Payment Methods Tab
+- Full payment methods management
+- Drag-and-drop reordering
+- Add/Edit/Delete payment methods
+- Active/Inactive status toggle
+
+## Files Created
+
+1. **`AdminSettingsNew.tsx`**
+   - Main settings page with tab navigation
+   - Responsive layout (vertical/horizontal)
+
+2. **`settings/AdminSettingsGeneral.tsx`**
+   - General settings + Maintenance mode
+   - Handles app configuration
+
+3. **`settings/AdminSettingsSecurity.tsx`**
+   - Feature toggles
+   - Security settings
+
+4. **`settings/AdminSettingsPaymentMethods.tsx`**
+   - Wrapper for existing AdminPaymentMethods component
+
+## Files Modified
+
+1. **`App.tsx`**
+   - Removed `/admin/payment-methods` route
+   - Updated import to use `AdminSettingsNew`
+
+2. **`AdminSidebar.tsx`**
+   - Removed "Payment Methods" menu item
+   - Consolidated under Settings
+
+3. **`AdminPaymentMethods.tsx`**
+   - Changed heading from h1 to h4 for tab context
+
+## UI/UX Improvements
+
+### Desktop
+- Vertical tabs on the left (fixed width: 256px)
+- Large content area on the right
+- Clear visual separation
+- Icons + text labels
+
+### Mobile
+- Horizontal scrollable tabs at top
+- Full-width content below
+- Icons + text labels visible
+- Touch-friendly tap targets
+
+### Responsive Breakpoint
+- Mobile: `< 768px` (md breakpoint)
+- Desktop: `≥ 768px`
+
+## Benefits
+
+1. **Cleaner Navigation**
+   - Reduced sidebar clutter
+   - Grouped related settings
+   - Better information architecture
+
+2. **Better UX**
+   - All settings in one place
+   - No page navigation needed
+   - Faster access to configuration
+
+3. **Scalability**
+   - Easy to add new tabs
+   - Modular component structure
+   - Clear separation of concerns
+
+## Testing
+
+### Desktop
+- [x] Vertical tabs display correctly
+- [x] Tab switching works
+- [x] All settings save properly
+- [x] Icons and labels visible
+
+### Mobile
+- [x] Horizontal scrollable tabs
+- [x] Tab switching works
+- [x] Content responsive
+- [x] Touch targets adequate
+
+## Future Enhancements
+
+Potential additions:
+- Notifications tab (Email/Push settings)
+- Integrations tab (Third-party services)
+- Appearance tab (Theme, branding)
+- Advanced tab (Developer settings)