feat(mobile): stage 10 - bulletin board (group detail '公告' tab)

- new BulletinListMobile.vue: pinned section + normal list + publish button
  + unread dots + realtime subscription + mark-all-read
- new BulletinPostSheetMobile.vue: 3-in-1 bottom sheet (detail / edit / create)
  with priority/pinned/expires + permission-based edit/delete (owner/admin/creator)
- GroupViewMobile: add '公告' tab (after 动态), wire BulletinListMobile
- reuses uat bulletin store (posts/pinnedPosts/normalPosts/isRead/create/update/remove)

build verified: vue-tsc + vite build pass

frontend/src/components-mobile/bulletin/BulletinPostSheetMobile.vue

@@ -0,0 +1,276 @@
+<!-- src/components-mobile/bulletin/BulletinPostSheetMobile.vue -->
+<!-- 公告详情/编辑/创建 三合一底部面板 -->
+<!-- - post=null & editing=true → 创建 -->
+<!-- - post=非null & editing=false → 详情（含编辑/删除） -->
+<!-- - post=非null & editing=true → 编辑 -->
+<script setup lang="ts">
+import { computed, ref, watch } from 'vue'
+import { useBulletinStore } from '@/stores/bulletin'
+import { useGroupStore } from '@/stores/group'
+import { pb } from '@/api/pocketbase'
+import { BulletinPriorityMap } from '@/types'
+import type { BulletinPost, BulletinPriority } from '@/types'
+import { displayName } from '@/types'
+import { showSuccessToast, showFailToast } from 'vant'
+
+const props = defineProps<{
+  show: boolean
+  post: BulletinPost | null
+  editing: boolean
+  groupId: string
+}>()
+
+const emit = defineEmits<{
+  'update:show': [value: boolean]
+  'edit': [post: BulletinPost]
+  'delete': [post: BulletinPost]
+  'saved': []
+}>()
+
+const bulletinStore = useBulletinStore()
+const groupStore = useGroupStore()
+
+const visible = computed({
+  get: () => props.show,
+  set: (val) => emit('update:show', val)
+})
+
+// 表单
+const form = ref({
+  title: '',
+  content: '',
+  priority: 'normal' as BulletinPriority,
+  pinned: false,
+  expiresAt: ''
+})
+const saving = ref(false)
+
+// 是否创建模式
+const isCreate = computed(() => props.editing && !props.post)
+
+// 权限：群主/管理员可编辑删除
+const currentUserId = computed(() => pb.authStore.model?.id || '')
+const canManage = computed(() => {
+  if (!props.post) return false
+  if (groupStore.isGroupOwner) return true
+  if (groupStore.isGroupAdmin) return true
+  if (props.post.creator === currentUserId.value) return true
+  return false
+})
+
+// 打开时同步表单
+watch(() => props.show, (val) => {
+  if (!val) return
+  if (props.editing && props.post) {
+    // 编辑模式：填充现有数据
+    form.value = {
+      title: props.post.title,
+      content: props.post.content,
+      priority: props.post.priority,
+      pinned: props.post.pinned,
+      expiresAt: props.post.expiresAt || ''
+    }
+  } else if (isCreate.value) {
+    // 创建模式：清空
+    form.value = { title: '', content: '', priority: 'normal', pinned: false, expiresAt: '' }
+  }
+})
+
+async function handleSubmit() {
+  if (!form.value.title.trim()) {
+    showFailToast('请输入标题')
+    return
+  }
+  if (!form.value.content.trim()) {
+    showFailToast('请输入内容')
+    return
+  }
+  saving.value = true
+  try {
+    const payload = {
+      title: form.value.title.trim(),
+      content: form.value.content.trim(),
+      priority: form.value.priority,
+      pinned: form.value.pinned,
+      expiresAt: form.value.expiresAt || undefined
+    }
+    if (isCreate.value) {
+      await bulletinStore.create({ group: props.groupId, ...payload })
+      showSuccessToast('发布成功')
+    } else if (props.post) {
+      await bulletinStore.update(props.post.id, payload)
+      showSuccessToast('修改成功')
+    }
+    emit('saved')
+  } catch (e: any) {
+    showFailToast(e.message || '操作失败')
+  } finally {
+    saving.value = false
+  }
+}
+
+const priorityKeys = Object.keys(BulletinPriorityMap) as BulletinPriority[]
+
+function priorityType(p: string): any {
+  const map: Record<string, string> = { urgent: 'danger', high: 'warning', normal: 'primary', low: 'default' }
+  return map[p] || 'default'
+}
+
+function formatDate(dateStr: string): string {
+  return new Date(dateStr).toLocaleString('zh-CN', { month: 'short', day: 'numeric', hour: '2-digit', minute: '2-digit' })
+}
+</script>
+
+<template>
+  <van-popup
+    v-model:show="visible"
+    position="bottom"
+    round
+    closeable
+    :style="{ height: editing ? '80%' : '70%' }"
+  >
+    <div class="post-sheet">
+      <!-- 编辑/创建模式 -->
+      <template v-if="editing">
+        <div class="sheet-title">{{ isCreate ? '发布公告' : '编辑公告' }}</div>
+        <van-cell-group inset>
+          <van-field v-model="form.title" label="标题" placeholder="公告标题" required maxlength="100" />
+          <van-field
+            v-model="form.content"
+            type="textarea"
+            label="内容"
+            placeholder="公告正文（支持换行）"
+            rows="5"
+            autosize
+            required
+          />
+          <van-field name="priority" label="优先级">
+            <template #input>
+              <select v-model="form.priority" class="native-select">
+                <option v-for="p in priorityKeys" :key="p" :value="p">{{ BulletinPriorityMap[p] }}</option>
+              </select>
+            </template>
+          </van-field>
+          <van-cell title="置顶" center>
+            <template #right-icon>
+              <van-switch v-model="form.pinned" size="22px" />
+            </template>
+          </van-cell>
+          <van-field v-model="form.expiresAt" label="截止时间" placeholder="可选，如 2026-12-31" />
+        </van-cell-group>
+        <div class="sheet-actions">
+          <van-button type="primary" block round :loading="saving" @click="handleSubmit">
+            {{ isCreate ? '发布' : '保存' }}
+          </van-button>
+        </div>
+      </template>
+
+      <!-- 详情模式 -->
+      <template v-else-if="post">
+        <div class="detail-header">
+          <van-tag :type="priorityType(post.priority)" size="large">{{ BulletinPriorityMap[post.priority] }}</van-tag>
+          <van-tag v-if="post.pinned" type="warning" size="large">置顶</van-tag>
+          <span class="detail-time">{{ formatDate(post.created) }}</span>
+        </div>
+
+        <h2 class="detail-title">{{ post.title }}</h2>
+
+        <div class="detail-meta">
+          <span>发布人：{{ displayName(post.expand?.creator) }}</span>
+          <span v-if="post.expiresAt" class="detail-expire">截止：{{ formatDate(post.expiresAt) }}</span>
+        </div>
+
+        <div class="detail-content">{{ post.content }}</div>
+
+        <div v-if="canManage" class="detail-actions">
+          <van-button size="small" round icon="edit" @click="emit('edit', post)">编辑</van-button>
+          <van-button size="small" round plain type="danger" icon="delete-o" @click="emit('delete', post)">删除</van-button>
+        </div>
+      </template>
+    </div>
+  </van-popup>
+</template>
+
+<style scoped>
+.post-sheet {
+  display: flex;
+  flex-direction: column;
+  height: 100%;
+  overflow-y: auto;
+  padding: 16px 0 24px;
+}
+
+.sheet-title {
+  text-align: center;
+  font-size: 16px;
+  font-weight: 600;
+  padding: 8px 0 16px;
+}
+
+.native-select {
+  border: 1px solid var(--gg-border);
+  border-radius: var(--gg-radius-sm);
+  padding: 6px 10px;
+  font-size: 14px;
+  background: var(--gg-bg-card);
+  width: 100%;
+}
+
+.sheet-actions {
+  padding: 20px 16px 0;
+  margin-top: auto;
+}
+
+/* 详情 */
+.detail-header {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  padding: 0 16px 12px;
+}
+
+.detail-time {
+  font-size: 12px;
+  color: var(--gg-text-muted);
+  margin-left: auto;
+}
+
+.detail-title {
+  font-size: 20px;
+  font-weight: 700;
+  color: var(--gg-text);
+  margin: 0;
+  padding: 0 16px;
+  line-height: 1.4;
+}
+
+.detail-meta {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 12px;
+  font-size: 12px;
+  color: var(--gg-text-muted);
+  padding: 8px 16px 16px;
+}
+
+.detail-expire {
+  color: var(--gg-warning);
+}
+
+.detail-content {
+  font-size: 15px;
+  color: var(--gg-text);
+  line-height: 1.7;
+  padding: 0 16px;
+  white-space: pre-wrap;
+  word-break: break-word;
+}
+
+.detail-actions {
+  display: flex;
+  gap: 10px;
+  justify-content: center;
+  padding: 24px 16px 0;
+  margin-top: auto;
+}
+</style>