Set up RSpec test framework

- Add rspec-rails to the development/test group
- Generate RSpec config (.rspec, spec_helper, rails_helper)
- Add home page request spec as a smoke test
- Stop ignoring .rspec so test config is tracked

Gemfile.lock

@@ -95,6 +95,7 @@ GEM
     debug (1.11.1)
       irb (~> 1.10)
       reline (>= 0.3.8)
+    diff-lcs (1.6.2)
     dotenv (3.2.0)
     drb (2.2.3)
     ed25519 (1.4.0)
@@ -243,6 +244,23 @@ GEM
     regexp_parser (2.12.0)
     reline (0.6.3)
       io-console (~> 0.5)
+    rspec-core (3.13.6)
+      rspec-support (~> 3.13.0)
+    rspec-expectations (3.13.5)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-mocks (3.13.8)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-rails (8.0.4)
+      actionpack (>= 7.2)
+      activesupport (>= 7.2)
+      railties (>= 7.2)
+      rspec-core (>= 3.13.0, < 5.0.0)
+      rspec-expectations (>= 3.13.0, < 5.0.0)
+      rspec-mocks (>= 3.13.0, < 5.0.0)
+      rspec-support (>= 3.13.0, < 5.0.0)
+    rspec-support (3.13.7)
     rubocop (1.86.1)
       json (~> 2.3)
       language_server-protocol (~> 3.17.0.2)
@@ -346,6 +364,7 @@ DEPENDENCIES
   propshaft
   puma (>= 5.0)
   rails (~> 8.1.3)
+  rspec-rails
   rubocop-rails-omakase
   solid_cable
   solid_cache