Merge pull request '결제 전환 목표 아키텍처 정의 (1/2) (2/2)' (#6) from forge/iss-87190c9836ac-attempt-1 into main

.forge/iss-5a912ed79baf-attempt-3.md

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+# iss-5a912ed79baf-attempt-3
+
+Forge 이슈 작업 브랜치 `forge/iss-5a912ed79baf-attempt-3`.

.forge/iss-87190c9836ac-attempt-1.md

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+# iss-87190c9836ac-attempt-1
+
+Forge 이슈 작업 브랜치 `forge/iss-87190c9836ac-attempt-1`.

docs/architecture/package-map.md

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+# Package Responsibility Map
+
+| Package        | Responsibility                                  | Forbidden Dependencies |
+|----------------|------------------------------------------------|------------------------|
+| controller     | Handles user input and orchestrates payment    | domain                 |
+| service        | Contains business logic for payment processing  | integration            |
+| repository     | Data access layer for payment records           | service                |
+| domain         | Defines the core domain models and business rules| controller             |
+| integration     | Communicates with external payment gateways     | domain, service        |

docs/architecture/transaction-sequence.md

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+```mermaid
+sequenceDiagram
+    participant User
+    participant PaymentService
+    participant PaymentGateway
+    participant Database
+
+    %% Normal Flow
+    User->>PaymentService: Initiate Payment
+    PaymentService->>Database: Store Transaction
+    Database-->>PaymentService: Transaction Stored
+    PaymentService->>PaymentGateway: Process Payment
+    PaymentGateway-->>PaymentService: Payment Success
+    PaymentService->>Database: Update Transaction Status
+    Database-->>PaymentService: Transaction Updated
+    PaymentService-->>User: Payment Success
+
+    %% External Failure Flow
+    User->>PaymentService: Initiate Payment
+    PaymentService->>Database: Store Transaction
+    Database-->>PaymentService: Transaction Stored
+    PaymentService->>PaymentGateway: Process Payment
+    PaymentGateway-->>PaymentService: Payment Failure
+    PaymentService->>Database: Rollback Transaction
+    Database-->>PaymentService: Transaction Rolled Back
+    PaymentService-->>User: Payment Failure
+
+    %% DB Failure Flow
+    User->>PaymentService: Initiate Payment
+    PaymentService->>Database: Store Transaction
+    Database-->>PaymentService: Transaction Store Failure
+    PaymentService-->>User: Payment Failure
+
+    %% Commit & Rollback
+    Note over User, PaymentService: 
+    commit --> PaymentService
+    rollback --> PaymentService
+```