feat: integrate PHPStan, Rector and Pint code quality tools (#13)

* feat: integrate PHPStan, Rector and Pint code quality tools

- Add larastan, rector, and rector-laravel dev dependencies
- Configure PHPStan at max level with Larastan extension
- Configure Rector with Laravel sets and code quality rules
- Configure Pint with strict rules (final_class, strict_types)
- Add composer scripts: lint, test:lint, test:types, test:unit
- Add GitHub Actions workflow for CI on push/PR
- Apply code style fixes across all files

* docs: add code quality section to README

.github/workflows/tests.yml

@@ -0,0 +1,55 @@
+name: tests
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  ci:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: 8.3
+          tools: composer:v2
+          coverage: xdebug
+
+      - name: Install Dependencies
+        run: composer install --no-interaction --prefer-dist --optimize-autoloader
+
+      - name: Copy Environment File
+        run: cp .env.example .env
+
+      - name: Generate Application Key
+        run: php artisan key:generate
+
+      - name: Create Database
+        run: touch database/database.sqlite
+
+      - name: Rector Cache
+        uses: actions/cache@v4
+        with:
+          path: /tmp/rector
+          key: ${{ runner.os }}-rector-${{ hashFiles('composer.lock') }}
+          restore-keys: ${{ runner.os }}-rector-
+      - run: mkdir -p /tmp/rector
+
+      - name: PHPStan Cache
+        uses: actions/cache@v4
+        with:
+          path: /tmp/phpstan
+          key: ${{ runner.os }}-phpstan-${{ hashFiles('composer.lock') }}
+          restore-keys: ${{ runner.os }}-phpstan-
+      - run: mkdir -p /tmp/phpstan
+
+      - name: Tests
+        run: composer test