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/dev

@@ -0,0 +1,16 @@
+#!/usr/bin/env sh
+
+if ! gem list foreman -i --silent; then
+  echo "Installing foreman..."
+  gem install foreman
+fi
+
+# Default to port 3000 if not specified
+export PORT="${PORT:-3000}"
+
+# Let the debug gem allow remote connections,
+# but avoid loading until `debugger` is called
+export RUBY_DEBUG_OPEN="true"
+export RUBY_DEBUG_LAZY="true"
+
+exec foreman start -f Procfile.dev "$@"