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

.gitea/workflows/build-iso.yaml

@@ -23,14 +23,14 @@ jobs:
       
       - name: Generate all recipes
         run: |
-          cd scripts
+          cd recipe-generator
           python3 generate_recipe.py \
             --manifest recipes_manifest.yaml \
             --output-dir ../recipes/
       
       - name: Validate recipes (strict mode)
         run: |
-          cd scripts
+          cd recipe-generator
           python3 generate_recipe.py --validate ../recipes/*.cfg --strict
   
   build-iso: