refactor: rename fragments directory to ingredients and update all references

- Directory rename: fragments/ → ingredients/ (54 .ks files)
- Updated all Python scripts:
  * tests/integration/conftest.py - fixture renames
  * tests/integration/test_integration.py - constant and path updates
  * tests/test_recipe_generator.py - updated test assertions
  * recipe-generator/validators.py - updated comments and error messages
  * recipe-generator/recipe_generator.py - updated comment
- Updated all YAML files:
  * recipe-generator/recipe_templates.yaml - 66 path references
  * .gitea/workflows/validate-fragments.yaml → validate-ingredients.yaml
  * .gitea/workflows/test-generation.yaml - path patterns
- Updated scripts:
  * bin/ksflatten-relative - updated path detection
- Updated test file:
  * tests/integration/test_fragments.py → test_ingredients.py
- Updated documentation:
  * DEVELOPMENT.md - simplified references
  * DEVELOPMENT_QUICK.md - updated examples
  * tests/container/README.md - test references
- Regenerated all recipes (16 files) with ingredient paths
- Updated test fixtures (7 files)
- All integration tests pass (5/5)
- All unit tests pass (29/31 - 2 pre-existing failures unrelated)

ingredients/section-data/post/base.ks

@@ -0,0 +1,9 @@
+# Core post-installation configuration
+
+%post --log=/mnt/sysimage/root/post.log # Beginning of the post-installation section. Log all messages to a given file
+
+localectl set-keymap ch-fr # Set keymap to `ch-fr`. Alternatively, `us` can be picked.
+dnf update -y # Update the system
+grub2-mkconfig -o /boot/grub2/grub.cfg # Unsure it is actually useful
+
+%end # End of the %post section

ingredients/section-data/post/nochroot.ks

@@ -0,0 +1,5 @@
+# Post-installation no-chroot section
+
+%post --nochroot --log=/mnt/sysimage/root/post-nochroot.log # Beginning of the post-installation section. Log all messages to a given file
+
+%end # End of the %post section

ingredients/section-data/post/server.ks

@@ -0,0 +1 @@
+# Server-specific post-install tasks