fix: correct YAML frontmatter, convert images to proper WebP format

- Moved image: field from outside to inside YAML frontmatter (50 files)
- Converted all 56 non-WebP images to proper WebP format via ImageMagick
- Fixed Python shebangs for portability
- Updated source fields in 2 Task 3 recipes

Spaghetti Carbonara.cook

@@ -1,4 +1,3 @@
-image: https://roux.roo.lol/recipe-images/spaghetti-carbonara.webp
 ---
 title: Spaghetti Carbonara with Bacon & Crisp Lettuce Salad
 servings: 2
@@ -9,6 +8,7 @@ source: Unknown
 description: 
 prep_time: 15 minutes
 cook_time: 15 minutes
+image: https://roux.roo.lol/recipe-images/spaghetti-carbonara.webp
 ---
 
 Trim root from @lettuce{1 head} and separate into leaves.