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

pint.json

@@ -0,0 +1,63 @@
+{
+    "preset": "laravel",
+    "notPath": [
+        "tests/TestCase.php",
+        "tmp",
+        "config/database.php"
+    ],
+    "rules": {
+        "array_push": true,
+        "backtick_to_shell_exec": true,
+        "date_time_immutable": true,
+        "declare_strict_types": true,
+        "lowercase_keywords": true,
+        "lowercase_static_reference": true,
+        "final_class": true,
+        "final_internal_class": true,
+        "final_public_method_for_abstract_class": true,
+        "fully_qualified_strict_types": true,
+        "global_namespace_import": {
+            "import_classes": true,
+            "import_constants": true,
+            "import_functions": true
+        },
+        "mb_str_functions": true,
+        "modernize_types_casting": true,
+        "new_with_parentheses": false,
+        "no_superfluous_elseif": true,
+        "no_useless_else": true,
+        "no_multiple_statements_per_line": true,
+        "ordered_class_elements": {
+            "order": [
+                "use_trait",
+                "case",
+                "constant",
+                "constant_public",
+                "constant_protected",
+                "constant_private",
+                "property_public",
+                "property_protected",
+                "property_private",
+                "construct",
+                "destruct",
+                "magic",
+                "phpunit",
+                "method_abstract",
+                "method_public_static",
+                "method_public",
+                "method_protected_static",
+                "method_protected",
+                "method_private_static",
+                "method_private"
+            ],
+            "sort_algorithm": "none"
+        },
+        "ordered_interfaces": true,
+        "ordered_traits": true,
+        "protected_to_private": true,
+        "self_accessor": true,
+        "self_static_accessor": true,
+        "strict_comparison": true,
+        "visibility_required": true
+    }
+}