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>

docs/development/database-seeder/makefile-database-seeder.md

@@ -171,7 +171,7 @@ migrate-status:
 
 backup-db:
 	@echo Creating database backup...
-	@$(PYTHON) scripts/backup_database.py
+	@$(PYTHON) scripts/seed/backup_database.py
 
 seed:
 	@echo Seeding database with comprehensive test data...