Add: Replace All option to text import UI

- Add replaceAll checkbox to ImportText view with warning
- Pass replaceAll parameter to import service
- Allows complete product catalog replacement via text import
- Enhanced documentation for unit types and variant collections

LittleShop/Areas/Admin/Controllers/ProductsController.cs

@@ -252,7 +252,7 @@ public class ProductsController : Controller
 
     [HttpPost]
     [ValidateAntiForgeryToken]
-    public async Task<IActionResult> ImportText(string textContent, IFormFile? file)
+    public async Task<IActionResult> ImportText(string textContent, IFormFile? file, bool replaceAll = false)
     {
         string importText = textContent;
 
@@ -277,7 +277,7 @@ public class ProductsController : Controller
 
         try
         {
-            var result = await _importService.ImportFromHumanTextAsync(importText);
+            var result = await _importService.ImportFromHumanTextAsync(importText, replaceAll);
             ViewData["ImportResult"] = result;
             return View("ImportResult", result);
         }

LittleShop/Areas/Admin/Views/Products/ImportText.cshtml

@@ -56,6 +56,18 @@
                         </div>
                     </div>
 
+                    <div class="mb-3">
+                        <div class="form-check">
+                            <input type="checkbox" name="replaceAll" id="replaceAll" class="form-check-input" value="true" />
+                            <label for="replaceAll" class="form-check-label">
+                                <strong class="text-danger">Replace All</strong> - Delete all existing products, variants, and categories before import
+                            </label>
+                        </div>
+                        <div class="form-text text-danger">
+                            <i class="fas fa-exclamation-triangle"></i> <strong>Warning:</strong> This will permanently delete ALL existing product data! This action cannot be undone.
+                        </div>
+                    </div>
+
                     <div class="mb-3">
                         <button type="submit" class="btn btn-primary">
                             <i class="fas fa-upload"></i> Import Products
@@ -121,11 +133,16 @@ stock: 50
 
                 <p class="small mt-3"><strong>Weight Units:</strong></p>
                 <ul class="small mb-0">
+                    <li><code>Unit</code> - For individual items (tablets, etc.)</li>
                     <li><code>Grams</code> (default)</li>
                     <li><code>Kilograms</code></li>
                     <li><code>Pounds</code></li>
                     <li><code>Ounces</code></li>
                 </ul>
+
+                <p class="small mt-3"><strong>Variant Collections:</strong></p>
+                <p class="small">Add after product name to link to variant collection:</p>
+                <code class="small"># Product Name; Weights - Standard</code>
             </div>
         </div>