Feature: Human-Readable Text Format Product Import

Implemented a new text-based import format for bulk product imports that is
easier to read, write, and version control compared to CSV format.

## New Features

### Import Service (ProductImportService.cs)
- Added `ImportFromHumanTextAsync()` - Main text format parser
- Added `GenerateTemplateAsHumanText()` - Template generator
- Parser supports:
  - Product blocks starting with `#`
  - Descriptions between `<text>` tags (optional)
  - Key-value properties (category, price, weight, unit, stock)
  - Variants (lines starting with `-`)
  - Multi-buy offers (lines starting with `+`)
  - Variant collections (optional, after product name)

### Admin UI
- New controller actions:
  - `ImportText()` - GET: Show import form
  - `ImportText(textContent, file)` - POST: Process import
  - `DownloadTextTemplate()` - Download .txt template
- New view: `ImportText.cshtml`
  - Textarea for pasting text
  - File upload for .txt files
  - Format documentation sidebar
  - Links to CSV import and template downloads
- Updated `Index.cshtml` with dropdown menu for import options

### Template & Documentation
- Created `docs/ProductImportTemplate.txt` with 7 example products
- Demonstrates all format features:
  - Products with/without descriptions
  - Variants with stock levels
  - Multi-buy pricing tiers
  - Multiple weight units

## Text Format Specification

```
# Product Name; OptionalVariantCollection
<text>
Multi-line description (optional)
</text>
category: CategoryName
price: 10.00
weight: 100
unit: Grams
stock: 50

- Variant1; 8.00; 50
- Variant2; 12.00; 30

+ Multi-buy1; 2; 19.00
+ Multi-buy2; 3; 25.00
```

## Benefits
- ✅ Git-friendly (easy to diff and version)
- ✅ Human-readable and editable
- ✅ Supports all product features
- ✅ Multi-line descriptions
- ✅ Clear structure with # delimiters
- ✅ Optional fields (description, variants, multi-buys)
- ✅ Comprehensive error reporting

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

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

LittleShop/Areas/Admin/Controllers/ProductsController.cs

@@ -244,6 +244,58 @@ public class ProductsController : Controller
         return File(Encoding.UTF8.GetBytes(templateContent), "text/csv", fileName);
     }
 
+    // Human-Readable Text Format Import
+    public IActionResult ImportText()
+    {
+        return View();
+    }
+
+    [HttpPost]
+    [ValidateAntiForgeryToken]
+    public async Task<IActionResult> ImportText(string textContent, IFormFile? file)
+    {
+        string importText = textContent;
+
+        // If file uploaded, use file content instead of textarea
+        if (file != null && file.Length > 0)
+        {
+            if (!file.FileName.EndsWith(".txt", StringComparison.OrdinalIgnoreCase))
+            {
+                ModelState.AddModelError("", "Only .txt files are supported for text format import");
+                return View();
+            }
+
+            using var reader = new StreamReader(file.OpenReadStream());
+            importText = await reader.ReadToEndAsync();
+        }
+
+        if (string.IsNullOrWhiteSpace(importText))
+        {
+            ModelState.AddModelError("", "Please provide text content or upload a .txt file");
+            return View();
+        }
+
+        try
+        {
+            var result = await _importService.ImportFromHumanTextAsync(importText);
+            ViewData["ImportResult"] = result;
+            return View("ImportResult", result);
+        }
+        catch (Exception ex)
+        {
+            ModelState.AddModelError("", $"Import failed: {ex.Message}");
+            return View();
+        }
+    }
+
+    public IActionResult DownloadTextTemplate()
+    {
+        var templateContent = _importService.GenerateTemplateAsHumanText();
+        var fileName = "product_import_template.txt";
+
+        return File(Encoding.UTF8.GetBytes(templateContent), "text/plain", fileName);
+    }
+
     [HttpGet]
     public async Task<IActionResult> GetVariantCollection(Guid id)
     {