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>

app/templates/admin/inventory.html

@@ -23,6 +23,13 @@
             width='w-80'
         ) }}
         {{ refresh_button(loading_var='loading', onclick='refresh()', variant='secondary') }}
+        <button
+            @click="showImportModal = true"
+            class="flex items-center px-4 py-2 text-sm font-medium leading-5 text-white transition-colors duration-150 bg-purple-600 border border-transparent rounded-lg hover:bg-purple-700 focus:outline-none focus:shadow-outline-purple"
+        >
+            <span x-html="$icon('upload', 'w-4 h-4 mr-2')"></span>
+            Import
+        </button>
     </div>
 {% endcall %}
 
@@ -456,6 +463,139 @@
     </div>
 </div>
 {% endcall %}
+
+<!-- Import Inventory Modal -->
+{% call modal_simple('importModal', 'Import Inventory', show_var='showImportModal', size='md') %}
+<div class="space-y-4">
+    <p class="text-sm text-gray-600 dark:text-gray-400">
+        Upload a TSV or CSV file to import inventory. Products are matched by EAN/GTIN.
+    </p>
+
+    <!-- File Format Info -->
+    <div class="p-3 bg-blue-50 dark:bg-blue-900/20 rounded-lg text-sm">
+        <p class="font-medium text-blue-800 dark:text-blue-200 mb-2">File Format:</p>
+        <p class="text-blue-700 dark:text-blue-300 text-xs font-mono mb-1">BIN    EAN    PRODUCT    QUANTITY</p>
+        <p class="text-blue-600 dark:text-blue-400 text-xs">
+            <strong>Required:</strong> BIN, EAN<br>
+            <strong>Optional:</strong> PRODUCT (display only), QUANTITY (defaults to 1 per row)
+        </p>
+    </div>
+
+    <form @submit.prevent="executeImport()">
+        <!-- Vendor Selection -->
+        <div class="mb-4">
+            <label class="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-1">
+                Vendor <span class="text-red-500">*</span>
+            </label>
+            <select
+                x-model="importForm.vendor_id"
+                required
+                class="w-full px-3 py-2 text-sm border border-gray-300 dark:border-gray-600 rounded-lg focus:border-purple-400 focus:outline-none dark:bg-gray-700 dark:text-gray-300"
+            >
+                <option value="">Select vendor...</option>
+                <template x-for="vendor in vendorsList" :key="vendor.id">
+                    <option :value="vendor.id" x-text="vendor.name + ' (' + vendor.vendor_code + ')'"></option>
+                </template>
+            </select>
+        </div>
+
+        <!-- Warehouse -->
+        <div class="mb-4">
+            <label class="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-1">
+                Warehouse
+            </label>
+            <input
+                type="text"
+                x-model="importForm.warehouse"
+                class="w-full px-3 py-2 text-sm border border-gray-300 dark:border-gray-600 rounded-lg focus:border-purple-400 focus:outline-none dark:bg-gray-700 dark:text-gray-300"
+                placeholder="strassen"
+            >
+        </div>
+
+        <!-- File Upload -->
+        <div class="mb-4">
+            <label class="block text-sm font-medium text-gray-700 dark:text-gray-300 mb-1">
+                File <span class="text-red-500">*</span>
+            </label>
+            <input
+                type="file"
+                @change="importForm.file = $event.target.files[0]"
+                accept=".tsv,.csv,.txt"
+                required
+                class="w-full px-3 py-2 text-sm border border-gray-300 dark:border-gray-600 rounded-lg focus:border-purple-400 focus:outline-none dark:bg-gray-700 dark:text-gray-300 file:mr-4 file:py-1 file:px-3 file:rounded file:border-0 file:text-sm file:font-medium file:bg-purple-100 file:text-purple-700 dark:file:bg-purple-900 dark:file:text-purple-300 hover:file:bg-purple-200"
+            >
+        </div>
+
+        <!-- Clear Existing Option -->
+        <div class="mb-4">
+            <label class="flex items-center">
+                <input
+                    type="checkbox"
+                    x-model="importForm.clear_existing"
+                    class="w-4 h-4 text-purple-600 border-gray-300 rounded focus:ring-purple-500"
+                >
+                <span class="ml-2 text-sm text-gray-700 dark:text-gray-300">
+                    Clear existing inventory for this warehouse before import
+                </span>
+            </label>
+        </div>
+
+        <!-- Import Result -->
+        <template x-if="importResult">
+            <div class="p-3 rounded-lg" :class="importResult.success ? 'bg-green-50 dark:bg-green-900/20' : 'bg-red-50 dark:bg-red-900/20'">
+                <p class="font-medium" :class="importResult.success ? 'text-green-800 dark:text-green-200' : 'text-red-800 dark:text-red-200'">
+                    <span x-text="importResult.success ? 'Import Successful!' : 'Import Failed'"></span>
+                </p>
+                <template x-if="importResult.success">
+                    <div class="text-sm text-green-700 dark:text-green-300 mt-1">
+                        <p>Rows processed: <span x-text="importResult.total_rows"></span></p>
+                        <p>Entries created: <span x-text="importResult.entries_created"></span></p>
+                        <p>Entries updated: <span x-text="importResult.entries_updated"></span></p>
+                        <p>Total quantity: <span x-text="importResult.quantity_imported"></span></p>
+                        <template x-if="importResult.unmatched_gtins?.length > 0">
+                            <div class="mt-2">
+                                <p class="font-medium text-orange-600 dark:text-orange-400">
+                                    Unmatched GTINs (<span x-text="importResult.unmatched_gtins.length"></span>):
+                                </p>
+                                <ul class="text-xs mt-1 max-h-32 overflow-y-auto">
+                                    <template x-for="item in importResult.unmatched_gtins" :key="item.gtin">
+                                        <li class="font-mono" x-text="item.gtin + ' (' + item.quantity + ' units) - ' + item.product_name"></li>
+                                    </template>
+                                </ul>
+                            </div>
+                        </template>
+                    </div>
+                </template>
+                <template x-if="!importResult.success && importResult.errors?.length > 0">
+                    <ul class="text-sm text-red-700 dark:text-red-300 mt-1">
+                        <template x-for="error in importResult.errors" :key="error">
+                            <li x-text="error"></li>
+                        </template>
+                    </ul>
+                </template>
+            </div>
+        </template>
+
+        <div class="flex items-center justify-end gap-3 pt-4 border-t border-gray-200 dark:border-gray-700">
+            <button
+                type="button"
+                @click="closeImportModal()"
+                class="px-4 py-2 text-sm font-medium text-gray-700 dark:text-gray-300 bg-white dark:bg-gray-700 border border-gray-300 dark:border-gray-600 rounded-lg hover:bg-gray-50 dark:hover:bg-gray-600 transition-colors"
+            >
+                <span x-text="importResult?.success ? 'Close' : 'Cancel'"></span>
+            </button>
+            <button
+                type="submit"
+                :disabled="importing || !importForm.vendor_id || !importForm.file"
+                x-show="!importResult?.success"
+                class="px-4 py-2 text-sm font-medium text-white bg-purple-600 rounded-lg hover:bg-purple-700 transition-colors disabled:opacity-50"
+            >
+                <span x-text="importing ? 'Importing...' : 'Import'"></span>
+            </button>
+        </div>
+    </form>
+</div>
+{% endcall %}
 {% endblock %}
 
 {% block extra_scripts %}