Add Point of Sale system and tax rate lookup integration

POS System:
- Full POS interface with product grid, cart panel, and payment flow
- Product and category management with barcode scanning support
- Cash drawer operations and shift management
- Order history and receipt generation
- Thermal printer integration (ESC/POS protocol)
- Gift card support with purchase and redemption
- Inventory tracking with low stock alerts
- Customer selection and walk-in support

Tax Rate Integration:
- ZIP-to-state mapping for automatic state detection
- SST boundary data import for 24 member states
- Static rates for uniform-rate states (IN, MA, CT, etc.)
- Statewide jurisdiction fallback for simple lookups
- Tax rate suggestion in location editor with auto-apply
- Multiple data sources: SST, CDTFA, TX Comptroller, Avalara

UI Improvements:
- POS renders full-screen outside BusinessLayout
- Clear cart button prominently in cart header
- Tax rate limited to 2 decimal places
- Location tax rate field with suggestion UI

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -130,6 +130,8 @@ const PublicPage = React.lazy(() => import('./pages/PublicPage')); // Import Pub
 const BookingFlow = React.lazy(() => import('./pages/BookingFlow')); // Import Booking Flow
 const Locations = React.lazy(() => import('./pages/Locations')); // Import Locations management page
 const MediaGalleryPage = React.lazy(() => import('./pages/MediaGalleryPage')); // Import Media Gallery page
+const POS = React.lazy(() => import('./pages/POS')); // Import Point of Sale page
+const Products = React.lazy(() => import('./pages/Products')); // Import Products management page
 
 // Settings pages
 const SettingsLayout = React.lazy(() => import('./layouts/SettingsLayout'));
@@ -765,6 +767,18 @@ const AppContent: React.FC = () => {
           <Route path="/login" element={<Navigate to="/dashboard" replace />} />
           <Route path="/sign/:token" element={<ContractSigning />} />
 
+          {/* Point of Sale - Full screen mode outside BusinessLayout */}
+          <Route
+            path="/dashboard/pos"
+            element={
+              canAccess('can_access_pos') ? (
+                <POS />
+              ) : (
+                <Navigate to="/dashboard" />
+              )
+            }
+          />
+
           {/* Dashboard routes inside BusinessLayout */}
           <Route
             element={
@@ -989,6 +1003,17 @@ const AppContent: React.FC = () => {
                 )
               }
             />
+            {/* Products Management */}
+            <Route
+              path="/dashboard/products"
+              element={
+                canAccess('can_access_pos') ? (
+                  <Products />
+                ) : (
+                  <Navigate to="/dashboard" />
+                )
+              }
+            />
             {/* Settings Routes with Nested Layout */}
             {/* Owners have full access, staff need can_access_settings permission */}
             {canAccess('can_access_settings') ? (