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

app/assets/stylesheets/application.css

@@ -0,0 +1,10 @@
+/*
+ * This is a manifest file that'll be compiled into application.css.
+ *
+ * With Propshaft, assets are served efficiently without preprocessing steps. You can still include
+ * application-wide styles in this file, but keep in mind that CSS precedence will follow the standard
+ * cascading order, meaning styles declared later in the document or manifest will override earlier ones,
+ * depending on specificity.
+ *
+ * Consider organizing styles into separate files for maintainability.
+ */

app/assets/tailwind/application.css

@@ -0,0 +1 @@
+@import "tailwindcss";