Product Lock 工作日誌規格

# [{date}] {title}

### Context
- Branch: `feature/xxx`
- Agent: {執行工作的人}
- Lock version: {此工作階段前的版本}
- PLS before: {score}

### Goal
{一句話：此工作階段要完成什麼。}

### Changes

| Action | Target | Detail |
|--------|--------|--------|
| added | Entity: Payment | 4 fields: id, amount, userId, createdAt |
| modified | Feature: checkout | Added Stripe integration |
| removed | Feature: manualInvoice | Replaced by automated billing |

### Lock Delta
{product.lock.json 中變更了什麼（如有）。}

### Score Delta
- PLS: {before} → {after} ({+/-delta})
- Breakdown: D {before}→{after}, F {before}→{after}, I {before}→{after}, A {before}→{after}

### Review Findings
{此工作階段後的 AI 審查者結果。}

### Decisions
{做出的關鍵決策及原因。}

### Files
| Action | Path |
|--------|------|
| created | src/models/payment.ts |
| modified | src/routes/checkout.ts |
| deleted | src/routes/manual-invoice.ts |

### Next
{下一個工作階段應接續的工作。}

### Context
- Branch: `feature/payment-system`
- Agent: Claude (Opus 4)
- Lock version: 1.2.0
- PLS before: 145

### Goal
Add payment processing with Stripe so Members can pay for premium features.

### Changes

| Action | Target | Detail |
|--------|--------|--------|
| added | Entity: Payment | id, amount, currency, userId, status, createdAt |
| added | Entity: Subscription | id, planId, userId, startDate, endDate |
| added | Feature: createPayment | Stripe checkout session creation |
| added | Feature: cancelSubscription | Self-service cancellation |
| modified | Feature: signup | Now creates free-tier Subscription |
| added | Actor: Subscriber | Paying member with premium access |
| added | Permission: Subscriber | createPayment, cancelSubscription, all Member perms |
| added | Denied: refundPayment | Refunds handled manually by admin |

### Review Findings

Reviewer: Claude (Sonnet 4.5)
Status: PASS (2 warnings)

- [PASS] Entity Payment — model exists with correct fields
- [PASS] Feature createPayment — POST /api/payments endpoint
- [WARN] Undeclared entity: PaymentLog (exists in code, not in lock)
- [WARN] Undeclared feature: retryPayment (exists in code, not in lock)

### Review Findings

No review conducted this session.

### Files

| Action | Path |
|--------|------|
| created | prisma/migrations/003_add_payment.sql |
| created | src/models/payment.ts |
| created | src/models/subscription.ts |
| created | src/routes/payments.ts |
| modified | src/routes/auth.ts |
| modified | src/middleware/permissions.ts |
| modified | prisma/schema.prisma |
| deleted | src/routes/legacy-billing.ts |

### Lock Delta

Lock updated: 1.2.0 → 1.3.0

Added:
- Entity: Payment [id, amount, currency, userId, status, createdAt]
- Entity: Subscription [id, planId, userId, startDate, endDate]
- Feature: createPayment
- Feature: cancelSubscription
- Actor: Subscriber
- Denied: refundPayment — "Refunds handled manually by admin"

Modified:
- Feature: signup (now includes subscription creation)
- Permission: Member → added cancelSubscription

Removed:
- (none)

### Score Delta

- PLS: 145 → 172 (+27)
- Level: Moderate → Complex
- Breakdown:
  - D: 79.2 → 94.8 (+15.6) — 2 new entities
  - F: 34 → 38 (+4) — 2 new features + 2 existing
  - I: 22.5 → 27.5 (+5) — added payment stories
  - A: 9 → 11.7 (+2.7) — Subscriber role added

### Decisions

1. **Stripe over Paddle**: Stripe has better API for subscription management. Paddle bundles tax handling but we don't need it for MVP.

2. **No refunds in v1**: Added to denied list. Manual refund via Stripe dashboard is sufficient. Automated refunds add liability and edge cases (partial refunds, proration).

3. **Subscription as separate entity**: Could have been a field on User, but Subscription has its own lifecycle (start, end, cancel, renew) that justifies a separate entity.

### Next

- [ ] Implement webhook handler for Stripe events (payment_intent.succeeded, subscription.canceled)
- [ ] Add PaymentLog to lock or remove from codebase (reviewer warning)
- [ ] Write stories for payment flow and add to lock
- [ ] Run full review after webhook implementation

### Commits

| Hash | Message |
|------|---------|
| a1b2c3d | feat: add Payment and Subscription models |
| e4f5g6h | feat: implement Stripe checkout endpoint |
| i7j8k9l | fix: permission middleware for Subscriber role |
| m0n1o2p | chore: update product.lock.json to v1.3.0 |

Continues from `2026-02-14-setup-stripe-integration.md`.
See `2026-02-12-define-payment-entities.md` for schema decisions.