ci(github): add PR title validation workflow

.github/pull-request-guide.md

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+# Pull Request 작성 가이드
+
+제목 형식 : `<type>(<scope>): <description>`
+
+## 규칙
+
+- **소문자**로 시작
+- **명령형 현재 시제** 사용 (add, 과거형 added가 아님)
+- 마침표 **없음**
+- **50자 이내** 권장
+
+## 🏷️ Types
+
+| Type       | 설명        | 예시                                            |
+|------------|-----------|-----------------------------------------------|
+| `feat`     | 새로운 기능 추가 | `feat(user): add email verification`          |
+| `fix`      | 버그 수정     | `fix(payment): resolve timeout error`         |
+| `docs`     | 문서 변경     | `docs(api): add OpenAPI spec`                 |
+| `style`    | 코드 스타일 변경 | `style(user): format with prettier`           |
+| `refactor` | 코드 리팩토링   | `refactor(order): extract calculation logic`  |
+| `test`     | 테스트 추가/수정 | `test(user): add authentication tests`        |
+| `chore`    | 기타 변경사항   | `chore(deps): upgrade Laravel to 12.1`        |
+| `perf`     | 성능 개선     | `perf(database): optimize user query`         |
+| `ci`       | CI/CD 변경  | `ci(github): add deployment workflow` |
+| `build`    | 빌드 시스템 변경 | `build(docker): update PHP to 8.5`            |
+| `revert`   | 이전 커밋 되돌리기 | `revert(payment): revert payment feature`     |
+
+## 🎯 Scopes
+
+| Scope                                   | 설명      |
+|-----------------------------------------|---------|
+| `user`, `product`, `order`, `payment`   | 도메인 관련  |
+| `auth`, `api`, `database`, `middleware` | 컴포넌트 관련 |
+| `service`, `controller`, `model`        | 레이어 관련  |
+| `docker`, `deps`, `config`, `github`    | 인프라 관련  |
+
+## 예시
+
+```
+feat(user): add email verification
+fix(payment): resolve timeout error
+refactor(order): extract calculation logic
+docs(api): add OpenAPI specification
+chore(deps): upgrade Laravel to 12.1
+```

.github/pull_request_template.md

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+<!--
+## PR Title Format
+Please ensure your PR title follows the Conventional Commits format:
+<type>(<scope>): <description>
+
+Types: feat, fix, docs, refactor, test, chore, perf, ci, build, style, revert
+Scopes: user, product, order, payment, auth, api, database, middleware, service, controller, model, docker, deps, config, github
+
+Examples:
+- feat(user): add social login support
+- fix(payment): resolve duplicate transaction issue
+- refactor(user): extract service layer from controllers
+-->

.github/workflows/pr-title-check.yml

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+name: "Lint PR"
+
+on:
+  pull_request_target:
+    types:
+      - opened
+      - edited
+      - synchronize
+      - labeled
+      - unlabeled
+
+permissions:
+  pull-requests: write
+  statuses: write
+
+jobs:
+  main:
+    name: Validate PR title
+    runs-on: ubuntu-latest
+    steps:
+      - uses: amannn/action-semantic-pull-request@v6
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          # Configure which types are allowed (Conventional Commits spec)
+          types: |
+            feat
+            fix
+            docs
+            style
+            refactor
+            perf
+            test
+            build
+            ci
+            chore
+            revert
+
+          # Scope is required for all PRs
+          requireScope: true
+
+          # Disallow uppercase scopes and multiple scopes
+          disallowScopes: |
+            [A-Z]+
+
+          # Work in progress PR support
+          wip: true
+
+          # Skip validation for PRs with these labels
+          ignoreLabels: |
+            bot
+            ignore-semantic-pull-request
+
+          # Ensure the subject doesn't start with an uppercase character
+          subjectPattern: ^[a-z].*$
+          subjectPatternError: |
+            The subject "{subject}" found in the pull request title "{title}"
+            didn't match the configured pattern. Please ensure that the subject
+            starts with a lowercase character.