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

bin/rubocop

@@ -0,0 +1,8 @@
+#!/usr/bin/env ruby
+require "rubygems"
+require "bundler/setup"
+
+# Explicit RuboCop config increases performance slightly while avoiding config confusion.
+ARGV.unshift("--config", File.expand_path("../.rubocop.yml", __dir__))
+
+load Gem.bin_path("rubocop", "rubocop")