feat(admin): implement full day-by-day schedule editor with live preview

## Features

### Admin Schedule Page (`packages/app/src/pages/admin/schedule.vue`)
- Interactive date-based slot editor for managing daily schedules
- Real-time slot editing: start/end times, capacity adjustments
- Slot deletion with conflict warnings when bookings exist
- Add new slots with modal dialog
- Live booking status display (booked count, people names)
- Publish/Save changes with sync feedback
- Revert unsaved changes with confirmation
- Skeleton loading states and empty state handling
- Responsive design with optimized mobile UX

### Backend Enhancements
- **New DTO** (`PublishDaySlotsDto`): Structured slot publishing with validation
  - Date string validation
  - Slot array with existing slot IDs for updates
  - Time and capacity validation per slot

- **Schedule Preview API** (`getSchedulePreview`):
  - Check for existing published slots
  - Fallback to active WeekTemplates for unpublished dates
  - Unified response format with isPublished flag

- **Publish Slots API** (`publishDaySlots`):
  - Atomic transaction for consistency
  - Update existing slots with new times/capacity
  - Create new slots from template data
  - Delete unpublished slots or set to CLOSED if bookings exist
  - Prevent capacity reduction below existing bookings
  - Returns all published slots for feedback

### State Management
- Enhanced admin store with schedule state
- Support for pending/unsaved slot changes
- Optimistic UI updates with server sync

### Documentation
- Comprehensive scheduling system architecture docs
- Quick reference for admin workflows
- Flow diagrams and state transitions
- Implementation guide for future maintenance

## Breaking Changes
None

## Testing Recommendations
- Create slots for future dates via schedule editor
- Verify booking prevention for locked/full slots
- Test capacity adjustments with existing bookings
- Confirm template-based schedule generation
- Verify transaction rollback on publish failures

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/shared/src/index.ts

@@ -35,6 +35,9 @@ export type {
   TimeSlot,
   TimeSlotWithBookingStatus,
   CreateManualSlotDto,
+  ScheduleSlotPreview,
+  PublishDaySlotItem,
+  PublishDaySlotsDto,
   Booking,
   BookingWithDetails,
   CreateBookingDto,

packages/shared/src/types/index.ts

@@ -2,7 +2,7 @@ export type { User, UserProfileResponse, UpdateProfileDto, UserStatsResponse } f
 export type { CardType, CreateCardTypeDto, UpdateCardTypeDto } from './card-type'
 export type { Membership, MembershipWithCardType } from './membership'
 export type { WeekTemplate, WeekTemplateInput } from './week-template'
-export type { TimeSlot, TimeSlotWithBookingStatus, CreateManualSlotDto } from './time-slot'
+export type { TimeSlot, TimeSlotWithBookingStatus, CreateManualSlotDto, ScheduleSlotPreview, PublishDaySlotItem, PublishDaySlotsDto } from './time-slot'
 export type { Booking, BookingWithDetails, CreateBookingDto } from './booking'
 export type { Order, OrderWithDetails, CreateOrderDto, PaymentParams, CreateOrderResponse } from './order'
 export type { StudioConfig, UpdateStudioConfigDto } from './studio'

packages/shared/src/types/time-slot.ts

@@ -27,3 +27,35 @@ export interface CreateManualSlotDto {
   readonly endTime: string
   readonly capacity?: number
 }
+
+/** 排课预览项（已发布的 TimeSlot 或模板派生的预览） */
+export interface ScheduleSlotPreview {
+  /** 已发布则有 ID，模板预览为 null */
+  readonly id: string | null
+  readonly date: string
+  readonly startTime: string
+  readonly endTime: string
+  readonly capacity: number
+  readonly bookedCount: number
+  readonly status: TimeSlotStatus
+  readonly source: TimeSlotSource
+  readonly templateId: string | null
+  /** true = DB 中已有 TimeSlot 记录 */
+  readonly isPublished: boolean
+}
+
+/** 发布某天排课时的单个时段 */
+export interface PublishDaySlotItem {
+  /** 保留/修改已有时段时传入 */
+  readonly existingSlotId?: string
+  readonly startTime: string
+  readonly endTime: string
+  readonly capacity: number
+}
+
+/** 发布某天排课的请求体 */
+export interface PublishDaySlotsDto {
+  /** YYYY-MM-DD */
+  readonly date: string
+  readonly slots: readonly PublishDaySlotItem[]
+}