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

.github/workflows/ci.yml

@@ -0,0 +1,67 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches: [ main ]
+
+jobs:
+  scan_ruby:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+
+      - name: Scan for common Rails security vulnerabilities using static analysis
+        run: bin/brakeman --no-pager
+      
+      - name: Scan for known security vulnerabilities in gems used
+        run: bin/bundler-audit
+      
+  scan_js:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+
+      - name: Scan for security vulnerabilities in JavaScript dependencies
+        run: bin/importmap audit
+
+  lint:
+    runs-on: ubuntu-latest
+    env:
+      RUBOCOP_CACHE_ROOT: tmp/rubocop
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+
+      - name: Prepare RuboCop cache
+        uses: actions/cache@v4
+        env:
+          DEPENDENCIES_HASH: ${{ hashFiles('.ruby-version', '**/.rubocop.yml', '**/.rubocop_todo.yml', 'Gemfile.lock') }}
+        with:
+          path: ${{ env.RUBOCOP_CACHE_ROOT }}
+          key: rubocop-${{ runner.os }}-${{ env.DEPENDENCIES_HASH }}-${{ github.ref_name == github.event.repository.default_branch && github.run_id || 'default' }}
+          restore-keys: |
+            rubocop-${{ runner.os }}-${{ env.DEPENDENCIES_HASH }}-
+
+      - name: Lint code for consistent style
+        run: bin/rubocop -f github
+