fix: Use active WooCommerce currency instead of hardcoded USD

Fixed Issues:
1. ✅ Currency hardcoded to USD in product forms
2. ✅ Edit page redirect to non-existent detail page

Changes:

🌍 Currency Integration (GeneralTab.tsx):
- Import getStoreCurrency() from @/lib/currency
- Get store currency data: symbol, decimals, position
- Replace hardcoded $ icon with dynamic store.symbol
- Use store.decimals for input step:
  * step="1" for zero-decimal currencies (IDR, JPY, etc.)
  * step="0.01" for decimal currencies (USD, EUR, etc.)
- Update placeholder based on decimals:
  * "0" for zero-decimal
  * "0.00" for decimal

Before:
- <DollarSign /> icon (always $)
- step="0.01" (always 2 decimals)
- placeholder="0.00" (always 2 decimals)

After:
- <span>{store.symbol}</span> (Rp, $, RM, etc.)
- step={store.decimals === 0 ? '1' : '0.01'}
- placeholder={store.decimals === 0 ? '0' : '0.00'}

🌍 Currency Display (index.tsx):
- Import formatMoney() from @/lib/currency
- Replace hardcoded $:
  * Before: ${parseFloat(product.regular_price).toFixed(2)}
  * After: formatMoney(product.regular_price)
- Now respects:
  * Currency symbol (Rp, $, RM, etc.)
  * Decimal places (0 for IDR, 2 for USD)
  * Thousand separator (. for IDR, , for USD)
  * Decimal separator (, for IDR, . for USD)
  * Position (left/right/left_space/right_space)

Examples:
- IDR: Rp 100.000 (no decimals, dot separator)
- USD: $100.00 (2 decimals, comma separator)
- MYR: RM 100.00 (2 decimals)

🔧 Edit Page Fix:
- Changed redirect after update:
  * Before: navigate(`/products/${id}`) → 404 (no detail page)
  * After: navigate('/products') → products list ✅

Result:
✅ Product forms use active WooCommerce currency
✅ Prices display with correct symbol and format
✅ Input fields respect currency decimals
✅ Edit page redirects to index after save
✅ Consistent with Orders module pattern

admin-spa/src/routes/Products/Edit.tsx

@@ -39,8 +39,8 @@ export default function ProductEdit() {
       queryClient.invalidateQueries({ queryKey: ['products'] });
       queryClient.invalidateQueries({ queryKey: ['products', id] });
       
-      // Navigate back to product detail or list
-      navigate(`/products/${id}`);
+      // Navigate back to products list
+      navigate('/products');
     },
     onError: (error: any) => {
       toast.error(error.message || __('Failed to update product'));