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

config/initializers/assets.rb

@@ -0,0 +1,7 @@
+# Be sure to restart your server when you modify this file.
+
+# Version of your assets, change this if you want to expire all your assets.
+Rails.application.config.assets.version = "1.0"
+
+# Add additional assets to the asset load path.
+# Rails.application.config.assets.paths << Emoji.images_path