feat: add inventory CSV import with warehouse/bin locations

- Add warehouse and bin_location columns to Inventory model
- Create inventory_import_service for bulk TSV/CSV import
- Add POST /api/v1/admin/inventory/import endpoint
- Add Import button and modal to inventory admin page
- Support both single-unit rows and explicit QUANTITY column

File format: BIN, EAN, PRODUCT (optional), QUANTITY (optional)
Products matched by GTIN/EAN, unmatched items reported.

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

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

static/admin/js/inventory.js

@@ -65,6 +65,7 @@ function adminInventory() {
         showAdjustModal: false,
         showSetModal: false,
         showDeleteModal: false,
+        showImportModal: false,
         selectedItem: null,
 
         // Form data
@@ -76,6 +77,17 @@ function adminInventory() {
             quantity: 0
         },
 
+        // Import form
+        importForm: {
+            vendor_id: '',
+            warehouse: 'strassen',
+            file: null,
+            clear_existing: false
+        },
+        importing: false,
+        importResult: null,
+        vendorsList: [],
+
         // Debounce timer
         searchTimeout: null,
 
@@ -144,6 +156,9 @@ function adminInventory() {
                 this.initVendorSelector();
             });
 
+            // Load vendors list for import modal
+            await this.loadVendorsList();
+
             // Check localStorage for saved vendor
             const savedVendorId = localStorage.getItem('inventory_selected_vendor_id');
             if (savedVendorId) {
@@ -501,6 +516,93 @@ function adminInventory() {
                 this.pagination.page = pageNum;
                 this.loadInventory();
             }
+        },
+
+        // ============================================================
+        // Import Methods
+        // ============================================================
+
+        /**
+         * Load vendors list for import modal
+         */
+        async loadVendorsList() {
+            try {
+                const response = await apiClient.get('/admin/vendors', { limit: 100 });
+                this.vendorsList = response.vendors || [];
+            } catch (error) {
+                adminInventoryLog.error('Failed to load vendors:', error);
+            }
+        },
+
+        /**
+         * Execute inventory import
+         */
+        async executeImport() {
+            if (!this.importForm.vendor_id || !this.importForm.file) {
+                Utils.showToast('Please select a vendor and file', 'error');
+                return;
+            }
+
+            this.importing = true;
+            this.importResult = null;
+
+            try {
+                const formData = new FormData();
+                formData.append('file', this.importForm.file);
+                formData.append('vendor_id', this.importForm.vendor_id);
+                formData.append('warehouse', this.importForm.warehouse || 'strassen');
+                formData.append('clear_existing', this.importForm.clear_existing);
+
+                const response = await fetch('/api/v1/admin/inventory/import', {
+                    method: 'POST',
+                    body: formData,
+                    headers: {
+                        'Authorization': `Bearer ${localStorage.getItem('access_token') || ''}`
+                    }
+                });
+
+                if (!response.ok) {
+                    const errorData = await response.json();
+                    throw new Error(errorData.detail || 'Import failed');
+                }
+
+                this.importResult = await response.json();
+
+                if (this.importResult.success) {
+                    adminInventoryLog.info('Import successful:', this.importResult);
+                    Utils.showToast(
+                        `Imported ${this.importResult.quantity_imported} units (${this.importResult.entries_created} new, ${this.importResult.entries_updated} updated)`,
+                        'success'
+                    );
+                    // Refresh inventory list
+                    await this.refresh();
+                } else {
+                    Utils.showToast('Import completed with errors', 'warning');
+                }
+            } catch (error) {
+                adminInventoryLog.error('Import failed:', error);
+                this.importResult = {
+                    success: false,
+                    errors: [error.message || 'Import failed']
+                };
+                Utils.showToast(error.message || 'Import failed', 'error');
+            } finally {
+                this.importing = false;
+            }
+        },
+
+        /**
+         * Close import modal and reset form
+         */
+        closeImportModal() {
+            this.showImportModal = false;
+            this.importResult = null;
+            this.importForm = {
+                vendor_id: '',
+                warehouse: 'strassen',
+                file: null,
+                clear_existing: false
+            };
         }
     };
 }