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/bundler-audit.yml

@@ -0,0 +1,5 @@
+# Audit all gems listed in the Gemfile for known security problems by running bin/bundler-audit.
+# CVEs that are not relevant to the application can be enumerated on the ignore list below.
+
+ignore:
+  - CVE-THAT-DOES-NOT-APPLY