refactor: Modularize recipe generator

- Split generate_recipe.py into cli.py, recipe_generator.py, validators.py, manifest.py
- Removed override logic - modifiers now add fragments rather than replace
- Added filename deduplication to prevent overwriting recipes
- Updated CI workflows and tests to use new module structure
- Made pykickstart a hard dependency
- Removed ingredients/ directory support (only fragments/*.ks now used)
- New layout: 5 modules (~990 lines) vs single 769-line file

tests/test_recipe_generator.py

@@ -7,7 +7,7 @@ import sys
 RECIPE_GENERATOR_DIR = Path(__file__).parent.parent / 'recipe-generator'
 sys.path.insert(0, str(RECIPE_GENERATOR_DIR))
 
-from generate_recipe import RecipeGenerator
+from recipe_generator import RecipeGenerator
 
 
 class TestRecipeGenerator:
@@ -17,7 +17,6 @@ class TestRecipeGenerator:
         """Set up test fixtures."""
         project_root = Path(__file__).parent.parent
         self.generator = RecipeGenerator(
-            project_root / 'ingredients',
             project_root / 'recipe-generator' / 'recipe_templates.yaml'
         )