📝 docs: Add documentation

docs/admin/commerce/coupon.md

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+<div v-pre>
+
+# Coupon Management
+
+Manage coupons in the system, including creating, editing, and enabling/disabling functions. Coupons provide purchase discounts for users.
+
+## Table Column Description
+
+### Enable
+Switch button to control whether the coupon is available. When off, users cannot use this coupon.
+
+### Name
+Coupon name for management identification.
+
+### Code
+Coupon redemption code that users enter during purchase to apply the coupon.
+
+### Type
+Coupon discount type:
+- **Percentage** - Discount by percentage (e.g., 10%)
+- **Amount** - Fixed amount discount (e.g., $50)
+
+### Discount
+Discount value:
+- Percentage type shows percentage (e.g., 10%)
+- Amount type shows currency amount (e.g., $50)
+
+### Count
+Displays three lines of information:
+- **Count** - Total available usage count (0 = unlimited)
+- **Remaining** - Remaining usage count
+- **Usage Times** - Times already used
+
+### Validity Period
+Coupon's valid time range:
+- Shows start time and end time
+- If only start time, shows single time
+- No restriction shows "--"
+
+## Table Operations
+
+### Edit
+Opens side drawer form to modify coupon information.
+
+### Delete
+Deletes coupon (requires confirmation), used coupons can also be deleted.
+
+### Batch Delete
+Deletes multiple selected coupons.
+
+## Coupon Form
+
+### Name (Required)
+Management name for the coupon, not displayed to users.
+
+### Custom Coupon Code (Optional)
+Custom redemption code, leave blank for system auto-generation.
+
+### Coupon Type (Required)
+Radio button to select type:
+- **Percentage Discount** - Discount by order amount percentage
+- **Amount Discount** - Fixed amount reduction
+
+### Discount Value (Required)
+Input based on type:
+- **Percentage**: Enter number 1-100 with % suffix
+- **Amount**: Enter currency amount
+
+### Specified Subscription (Optional)
+Multi-select dropdown to choose applicable product plans:
+- Leave blank for all products
+- Select specific products for those only
+
+### Start Time (Optional)
+Coupon activation time:
+- Use date picker
+- Cannot select past dates (before yesterday)
+- Leave blank for immediate effect
+
+### Expire Time (Optional)
+Coupon expiration time:
+- Use date picker
+- Leave blank for never expires
+
+### Max Usage Count (Optional)
+Total times the coupon can be used:
+- 0 or blank for unlimited
+- Automatically expires when count reached
+
+### Max Usage Count per User (Optional)
+Times a single user can use this coupon:
+- 0 or blank for unlimited
+- Prevents repeated use by single user
+
+## Filter Functions
+
+### Subscribe Filter
+Select product plan to view exclusive coupons for that product.
+
+### Keyword Search
+Search coupons by name or code.
+
+## Usage Scenarios
+
+### Scenario 1: Create New User Registration Coupon
+
+**Form Configuration**:
+- Name: New User Discount
+- Code: NEWUSER2024 (custom)
+- Type: Percentage Discount
+- Discount: 20%
+- Specified Subscription: Leave blank (all products)
+- Start Time: 2024-01-01
+- Expire Time: 2024-12-31
+- Max Usage Count: 0 (unlimited)
+- Max Usage Count per User: 1
+
+**Effect**: Each new user can use once, valid all year, 20% off all products.
+
+### Scenario 2: Create Limited-Time Promotion Coupon
+
+**Form Configuration**:
+- Name: Double 11 Promotion
+- Code: Leave blank (auto-generate)
+- Type: Amount Discount
+- Discount: $50
+- Specified Subscription: Select "Annual Plan"
+- Start Time: 2024-11-11 00:00
+- Expire Time: 2024-11-11 23:59
+- Max Usage Count: 100
+- Max Usage Count per User: 1
+
+**Effect**: First 100 users on Double 11 get $50 off annual plan, one per user.
+
+### Scenario 3: Create Exclusive VIP Coupon
+
+**Form Configuration**:
+- Name: VIP Exclusive
+- Code: VIP888 (custom)
+- Type: Percentage Discount
+- Discount: 30%
+- Specified Subscription: Select "Premium Plan"
+- Start Time: Leave blank
+- Expire Time: Leave blank
+- Max Usage Count: 0 (unlimited)
+- Max Usage Count per User: 0 (unlimited)
+
+**Effect**: VIP users can use unlimited times, 30% off premium plan.
+
+### Scenario 4: Create One-Time Coupon Code
+
+**Form Configuration**:
+- Name: Thank You Gift
+- Code: THANKS100 (custom)
+- Type: Amount Discount
+- Discount: $100
+- Specified Subscription: Leave blank (all products)
+- Start Time: Leave blank
+- Expire Time: Leave blank
+- Max Usage Count: 1
+- Max Usage Count per User: 1
+
+**Effect**: Single-use thank you coupon, first come first served.
+
+## Important Notes
+
+1. **Enable Control**: New coupons default to disabled, must manually enable for users
+2. **Code Uniqueness**: Custom codes must be unique, duplicates will fail
+3. **Auto-Generation**: Leave code blank for system to auto-generate random code
+4. **Product Restriction**: Specified subscriptions apply only to selected products
+5. **Time Range**: Start time cannot be in past, expire time can be blank
+6. **Usage Count**: 0 or blank means unlimited
+7. **User Limit**: Per-user limit prevents abuse
+8. **Delete Impact**: Deleting coupons doesn't affect already-used orders
+
+</div>