Merge pull request '결제 전환 목표 아키텍처 정의 (1/2) (1/2)' (#5) from forge/SPRING-ARC-QUALITY-1783831207-attempt-2 into main

.forge/iss-155aa95ea6df-attempt-2.md

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+# iss-155aa95ea6df-attempt-2
+
+Forge 이슈 작업 브랜치 `forge/iss-155aa95ea6df-attempt-2`.

.forge/iss-8fd82b653bff-attempt-1.md

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+# iss-8fd82b653bff-attempt-1
+
+Forge 이슈 작업 브랜치 `forge/iss-8fd82b653bff-attempt-1`.

docs/architecture/package-map.md

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+# Package Map
+
+| Package        | Responsibility                                      | Forbidden Dependencies |
+|----------------|----------------------------------------------------|------------------------|
+| controller     | Handle HTTP requests and responses                  | domain                 |
+| service        | Business logic and transaction management           | domain, integration     |
+| repository     | Data access and retrieval                           | service                 |
+| domain         | Core domain logic and entities                      | controller, service, repository |
+| integration     | External service communication                     | service                 |

docs/architecture/transaction-sequence.md

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+```mermaid
+sequenceDiagram
+    participant User as User
+    participant Checkout as Checkout Service
+    participant Payment as Payment Gateway
+    participant DB as Database
+
+    %% Normal flow
+    User->>Checkout: Initiate Checkout
+    Checkout->>DB: Save Order
+    DB-->>Checkout: Order Confirmation
+    Checkout->>Payment: Process Payment
+    Payment-->>Checkout: Payment Success
+    Checkout->>User: Payment Successful
+
+    %% External failure
+    User->>Checkout: Initiate Checkout
+    Checkout->>DB: Save Order
+    DB-->>Checkout: Order Confirmation
+    Checkout->>Payment: Process Payment
+    Payment-->>Checkout: Payment Failure
+    Checkout->>DB: Rollback Order
+    DB-->>Checkout: Order Rollback
+    Checkout->>User: Payment Failed
+
+    %% DB failure
+    User->>Checkout: Initiate Checkout
+    Checkout->>DB: Save Order
+    DB-->>Checkout: Order Confirmation
+    Checkout->>Payment: Process Payment
+    Payment-->>Checkout: Payment Success
+    Checkout->>DB: Commit Order
+    DB-->>Checkout: Error
+    Checkout->>DB: Rollback Order
+    DB-->>Checkout: Order Rollback
+    Checkout->>User: Payment Successful, Order Error
+```