Implement supplier product/price association & unify onboarding UI

MAJOR FEATURES IMPLEMENTED:

1. ✅ CRITICAL: Supplier Product/Price Association
   - Created SupplierProductManager component (438 lines)
   - Multi-select product picker from inventory
   - Price entry with unit of measure and min quantity
   - Expandable UI per supplier (collapsed by default)
   - Full CRUD operations via existing API hooks
   - Required for automatic Purchase Order (PO) creation
   - Warning shown if supplier has no products

2. ✅ Step Re-Ordering: Inventory Before Suppliers
   - Manual path: inventory-setup now comes BEFORE suppliers-setup
   - AI path: Already has inventory from sales data upload
   - Ensures products exist before supplier association
   - Critical workflow fix identified by user

3. ✅ UI/UX Unification
   - Unified badge styles across AI suggestions
   - Changed hardcoded colors to CSS variables
   - Consistent rounded-full badge design
   - Added flex-wrap for responsive badges

IMPLEMENTATION DETAILS:

SupplierProductManager.tsx (NEW - 438 lines):
- useSupplierPriceLists() - Fetch existing products for supplier
- useIngredients() - Fetch all available inventory items
- useCreate/Update/DeleteSupplierPriceList() mutations
- Expandable UI: Collapsed shows count, expanded shows management
- Product selection: Checkboxes with inline price forms
- Form fields: unit_price (required), unit_of_measure, min_order_quantity
- Validation: Price must be > 0, unit required
- Warning: Shows if no products added (blocks PO creation)

UnifiedOnboardingWizard.tsx:
- inventory-setup moved before suppliers-setup
- inventory-setup condition: dataSource === 'manual'
- suppliers-setup condition: Inventory exists (AI stockEntryCompleted OR manual inventoryCompleted)
- Ensures products always exist before supplier association

SuppliersSetupStep.tsx:
- Added SupplierProductManager import
- Changed supplier card layout from flex items-center to block
- Integrated ProductManager component into each supplier card
- Product management appears below contact info, above edit/delete

UploadSalesDataStep.tsx:
- Updated badge colors: blue-100/blue-800 → CSS variables
- Changed bg-[var(--bg-tertiary)] → bg-[var(--bg-primary)]
- Added flex-wrap to badge container
- Consistent rounded-full design

FLOW IMPROVEMENTS:

AI-Assisted Path:
Registration → Bakery Type → Data Source → Tenant Setup →
Upload Sales → Categorize → Enter Stock → **Suppliers (with products)** →
ML Training → Complete

Manual Path:
Registration → Bakery Type → Data Source → Tenant Setup →
**Inventory Setup → Suppliers (with products)** → Recipes → Processes →
ML Training → Complete

BENEFITS:
✅ Automatic PO creation now possible
✅ System knows supplier-product relationships
✅ Prices tracked for cost analysis
✅ Logical workflow (products before suppliers)
✅ Unified, consistent UI across onboarding
✅ Critical missing feature implemented

Build: Successful (21.73s)
Files: 4 changed (3 modified, 1 new)
Lines: +438 new component, ~50 lines modified

frontend/src/components/domain/onboarding/UnifiedOnboardingWizard.tsx

@@ -108,22 +108,28 @@ const OnboardingWizardContent: React.FC = () => {
       isConditional: true,
       condition: (ctx) => ctx.state.dataSource === 'ai-assisted' && ctx.state.categorizationCompleted,
     },
-    // Phase 2b: Core Data Entry
-    {
-      id: 'suppliers-setup',
-      title: t('onboarding:steps.suppliers.title', 'Proveedores'),
-      description: t('onboarding:steps.suppliers.description', 'Configura tus proveedores'),
-      component: SuppliersSetupStep,
-      isConditional: true,
-      condition: (ctx) => ctx.state.dataSource !== null,
-    },
+    // Phase 2b: Core Data Entry (Manual Path)
+    // IMPORTANT: Inventory must come BEFORE suppliers so suppliers can associate products
     {
       id: 'inventory-setup',
       title: t('onboarding:steps.inventory.title', 'Inventario'),
       description: t('onboarding:steps.inventory.description', 'Productos e ingredientes'),
       component: InventorySetupStep,
       isConditional: true,
-      condition: (ctx) => ctx.state.dataSource !== null,
+      condition: (ctx) =>
+        // Only show for manual path (AI path creates inventory earlier)
+        ctx.state.dataSource === 'manual',
+    },
+    {
+      id: 'suppliers-setup',
+      title: t('onboarding:steps.suppliers.title', 'Proveedores'),
+      description: t('onboarding:steps.suppliers.description', 'Configura tus proveedores'),
+      component: SuppliersSetupStep,
+      isConditional: true,
+      condition: (ctx) =>
+        // Show after inventory exists (either from AI or manual path)
+        (ctx.state.dataSource === 'ai-assisted' && ctx.state.stockEntryCompleted) ||
+        (ctx.state.dataSource === 'manual' && ctx.state.inventoryCompleted),
     },
     {
       id: 'recipes-setup',