feat: Sales Entry wizard now uses finished products dropdown

Sales Entry Wizard - Manual Entry Improvements:
- Replaced text input 'Nombre del producto' with dropdown selector
- Fetches finished products from inventory via inventoryService.getIngredients()
- Filters for finished_product category only
- Shows product name and price in dropdown options
- Auto-fills price when product is selected
- Loading state while fetching products
- Error handling if products fail to load
- Empty state if no finished products exist
- Disabled 'Agregar Producto' button while loading or if no products
- Fixed dark mode inputs with bg-[var(--bg-primary)] and text-[var(--text-primary)]

This is a CRITICAL improvement - products sold must come from inventory.

frontend/src/components/domain/unified-wizard/wizards/SalesEntryWizard.tsx

@@ -1,4 +1,4 @@
-import React, { useState } from 'react';
+import React, { useState, useEffect } from 'react';
 import { WizardStep, WizardStepProps } from '../../../ui/WizardModal/WizardModal';
 import {
   Edit3,
@@ -16,6 +16,7 @@ import {
 } from 'lucide-react';
 import { useTenant } from '../../../../stores/tenant.store';
 import { salesService } from '../../../../api/services/sales';
+import { inventoryService } from '../../../../api/services/inventory';
 
 // ========================================
 // STEP 1: Entry Method Selection
@@ -184,17 +185,42 @@ const EntryMethodStep: React.FC<EntryMethodStepProps> = ({ data, onDataChange, o
 // ========================================
 
 const ManualEntryStep: React.FC<EntryMethodStepProps> = ({ data, onDataChange, onNext }) => {
+  const { currentTenant } = useTenant();
   const [salesItems, setSalesItems] = useState(data.salesItems || []);
   const [saleDate, setSaleDate] = useState(
     data.saleDate || new Date().toISOString().split('T')[0]
   );
   const [paymentMethod, setPaymentMethod] = useState(data.paymentMethod || 'cash');
   const [notes, setNotes] = useState(data.notes || '');
+  const [products, setProducts] = useState<any[]>([]);
+  const [loadingProducts, setLoadingProducts] = useState(true);
+  const [error, setError] = useState<string | null>(null);
+
+  useEffect(() => {
+    fetchProducts();
+  }, []);
+
+  const fetchProducts = async () => {
+    if (!currentTenant?.id) return;
+
+    setLoadingProducts(true);
+    try {
+      const result = await inventoryService.getIngredients(currentTenant.id);
+      // Filter for finished products only
+      const finishedProducts = result.filter((p: any) => p.category === 'finished_product');
+      setProducts(finishedProducts);
+    } catch (err: any) {
+      console.error('Error fetching products:', err);
+      setError('Error al cargar los productos');
+    } finally {
+      setLoadingProducts(false);
+    }
+  };
 
   const handleAddItem = () => {
     setSalesItems([
       ...salesItems,
-      { id: Date.now(), product: '', quantity: 1, unitPrice: 0, subtotal: 0 },
+      { id: Date.now(), productId: '', product: '', quantity: 1, unitPrice: 0, subtotal: 0 },
     ]);
   };
 
@@ -202,8 +228,18 @@ const ManualEntryStep: React.FC<EntryMethodStepProps> = ({ data, onDataChange, o
     const updated = salesItems.map((item: any, i: number) => {
       if (i === index) {
         const newItem = { ...item, [field]: value };
+
+        // If product is selected, auto-fill price
+        if (field === 'productId') {
+          const selectedProduct = products.find((p: any) => p.id === value);
+          if (selectedProduct) {
+            newItem.product = selectedProduct.name;
+            newItem.unitPrice = selectedProduct.average_cost || selectedProduct.last_purchase_price || 0;
+          }
+        }
+
         // Auto-calculate subtotal
-        if (field === 'quantity' || field === 'unitPrice') {
+        if (field === 'quantity' || field === 'unitPrice' || field === 'productId') {
           newItem.subtotal = (newItem.quantity || 0) * (newItem.unitPrice || 0);
         }
         return newItem;
@@ -278,6 +314,13 @@ const ManualEntryStep: React.FC<EntryMethodStepProps> = ({ data, onDataChange, o
         </div>
       </div>
 
+      {error && (
+        <div className="p-3 bg-red-50 border border-red-200 rounded-lg text-red-700 text-sm flex items-start gap-2">
+          <AlertCircle className="w-4 h-4 mt-0.5 flex-shrink-0" />
+          <span>{error}</span>
+        </div>
+      )}
+
       {/* Sales Items */}
       <div className="space-y-3">
         <div className="flex items-center justify-between">
@@ -287,13 +330,25 @@ const ManualEntryStep: React.FC<EntryMethodStepProps> = ({ data, onDataChange, o
           </label>
           <button
             onClick={handleAddItem}
-            className="px-3 py-1.5 text-sm bg-[var(--color-primary)] text-white rounded-md hover:bg-[var(--color-primary)]/90 transition-colors"
+            disabled={loadingProducts || products.length === 0}
+            className="px-3 py-1.5 text-sm bg-[var(--color-primary)] text-white rounded-md hover:bg-[var(--color-primary)]/90 transition-colors disabled:opacity-50 disabled:cursor-not-allowed"
           >
             + Agregar Producto
           </button>
         </div>
 
-        {salesItems.length === 0 ? (
+        {loadingProducts ? (
+          <div className="flex items-center justify-center py-8">
+            <Loader2 className="w-6 h-6 animate-spin text-[var(--color-primary)]" />
+            <span className="ml-3 text-[var(--text-secondary)]">Cargando productos...</span>
+          </div>
+        ) : products.length === 0 ? (
+          <div className="text-center py-8 border-2 border-dashed border-[var(--border-secondary)] rounded-lg text-[var(--text-tertiary)]">
+            <Package className="w-8 h-8 mx-auto mb-2 opacity-50" />
+            <p>No hay productos terminados disponibles</p>
+            <p className="text-sm">Agrega productos al inventario primero</p>
+          </div>
+        ) : salesItems.length === 0 ? (
           <div className="text-center py-8 border-2 border-dashed border-[var(--border-secondary)] rounded-lg text-[var(--text-tertiary)]">
             <Package className="w-8 h-8 mx-auto mb-2 opacity-50" />
             <p>No hay productos agregados</p>
@@ -308,13 +363,18 @@ const ManualEntryStep: React.FC<EntryMethodStepProps> = ({ data, onDataChange, o
               >
                 <div className="grid grid-cols-12 gap-2 items-center">
                   <div className="col-span-12 sm:col-span-5">
-                    <input
+                    <select
-                      type="text"
+                      value={item.productId}
-                      placeholder="Nombre del producto"
+                      onChange={(e) => handleUpdateItem(index, 'productId', e.target.value)}
-                      value={item.product}
+                      className="w-full px-2 py-1.5 text-sm border border-[var(--border-secondary)] rounded focus:outline-none focus:ring-1 focus:ring-[var(--color-primary)] bg-[var(--bg-primary)] text-[var(--text-primary)]"
-                      onChange={(e) => handleUpdateItem(index, 'product', e.target.value)}
+                    >
-                      className="w-full px-2 py-1.5 text-sm border border-[var(--border-secondary)] rounded focus:outline-none focus:ring-1 focus:ring-[var(--color-primary)]"
+                      <option value="">Seleccionar producto...</option>
-                    />
+                      {products.map((product: any) => (
+                        <option key={product.id} value={product.id}>
+                          {product.name} - €{(product.average_cost || product.last_purchase_price || 0).toFixed(2)}
+                        </option>
+                      ))}
+                    </select>
                   </div>
                   <div className="col-span-4 sm:col-span-2">
                     <input