Set up Rails 8 application foundation

- Generate Rails 8.1 app with PostgreSQL and TailwindCSS
- Add docker-compose.yml (postgres:17) for local database
- Configure database.yml to connect to Dockerized Postgres via env vars
- Add Pages#home root route, application layout, and navbar partial

.rubocop.yml

@@ -0,0 +1,8 @@
+# Omakase Ruby styling for Rails
+inherit_gem: { rubocop-rails-omakase: rubocop.yml }
+
+# Overwrite or add rules to create your own house style
+#
+# # Use `[a, [b, c]]` not `[ a, [ b, c ] ]`
+# Layout/SpaceInsideArrayLiteralBrackets:
+#   Enabled: false