添加完整 CI/CD 流程

- Gitea Actions 配置 (.gitea/workflows/ci.yml)
- PHPUnit 测试框架 (composer.json, phpunit.xml)
- 示例测试用例 (tests/Unit, tests/Feature)
- .gitignore 配置

流程说明:
1. feature/* 分支 push → 部署测试环境 → 运行测试
2. 测试失败 → 自动回退 + 通知
3. 测试通过 → 自动合并到 main → 部署正式环境
4. main 分支 push → 直接部署正式环境

需要配置 Secrets:
- DEPLOY_KEY: SSH 私钥
- GITEA_TOKEN: 用于自动合并的 Token

phpunit.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
+         bootstrap="tests/bootstrap.php"
+         colors="true"
+         cacheDirectory=".phpunit.cache">
+    <testsuites>
+        <testsuite name="Unit">
+            <directory>tests/Unit</directory>
+        </testsuite>
+        <testsuite name="Feature">
+            <directory>tests/Feature</directory>
+        </testsuite>
+    </testsuites>
+    <source>
+        <include>
+            <directory suffix=".php">src</directory>
+            <directory suffix=".php">.</directory>
+            <exclude>vendor</exclude>
+            <exclude>tests</exclude>
+        </include>
+    </source>
+</phpunit>