refactor(scripts): reorganize scripts/ into seed/ and validate/ subfolders

Move 9 init/seed scripts into scripts/seed/ and 7 validation scripts
(+ validators/ subfolder) into scripts/validate/ to reduce clutter in
the root scripts/ directory. Update all references across Makefile,
CI/CD configs, pre-commit hooks, docs (~40 files), and Python imports.

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

.gitlab/merge_request_templates/default.md

@@ -20,7 +20,7 @@
 
 <!-- Describe how you tested these changes -->
 - [ ] Unit tests pass (`pytest tests/`)
-- [ ] Architecture validation passes (`python scripts/validate_architecture.py`)
+- [ ] Architecture validation passes (`python scripts/validate/validate_architecture.py`)
 - [ ] Manual testing performed
 
 ## Checklist