fix: image upload (add extension field) + ingredient groups

- Fix Mealie image upload 422: send required `extension` field in form data
- Parse ingredient groups from mindmegette (multiple div.ingredients
  containers with strong.ingredients-group titles)
- Show group headers in UI with dashed-border accent input
- Pass group markers through to Mealie as title-only ingredient entries

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/scraper.py

@@ -61,9 +61,16 @@ def _parse_mindmegette(soup: BeautifulSoup, url: str) -> dict:
     image_url = _og(soup, "og:image")
 
     # --- Ingredients ---
+    # Multiple div.ingredients containers may exist (one per group).
+    # Group title: <strong class="ingredients-group">A habaráshoz:</strong>
     ingredients = []
-    ing_container = soup.find("div", class_="ingredients")
-    if ing_container:
+    for ing_container in soup.find_all("div", class_="ingredients"):
+        # Check for a group title
+        group_el = ing_container.find("strong", class_="ingredients-group")
+        group_name = _text(group_el).rstrip(":").strip() if group_el else ""
+        if group_name:
+            ingredients.append({"group": group_name})
+
         for row in ing_container.find_all("div", class_="ingredients-meta"):
             # Actual HTML: <strong>qty</strong> <span>unit</span>
             #              <a class="ingredients-link">name</a> <small>(extra)</small>