Integrate fizzy-saas as vendored gem at saas/

- Update Gemfile.saas to use path: "saas" instead of GitHub source
- Update config/database.yml to reference local saas/ directory
- Update bin/setup to source saas/bin/setup directly
- Remove redundant dotfiles (ruby-version, gitignore, rubocop, github workflows)
- Add saas/db exclusions to root rubocop config

Gemfile.saas

@@ -6,7 +6,7 @@ git_source(:bc) { |repo| "https://github.com/basecamp/#{repo}" }
 gem "activeresource", require: "active_resource"
 gem "stripe", "~> 18.0"
 gem "queenbee", bc: "queenbee-plugin"
-gem "fizzy-saas", bc: "fizzy-saas"
+gem "fizzy-saas", path: "saas"
 gem "console1984", bc: "console1984"
 gem "audits1984", bc: "audits1984"