feat: game cover file upload + fix game visibility rules

- Change game cover field from URL text to file upload (PocketBase migration)
- AddGameDialog now supports drag-and-drop image upload instead of URL input
- Add getGameCoverUrl() helper using pb.files.getUrl() for cover display
- Fix games listRule/viewRule: group.members.id syntax doesn't work in PB 0.22,
  changed to group.members ~ @request.auth.id for correct member visibility
- Update changelog with all v0.3.5 entries

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/components/game/AddGameDialog.vue

@@ -4,6 +4,8 @@ import { addGame } from '@/api/games'
 import type { GamePlatform } from '@/types'
 import { ElMessage } from 'element-plus'
 import { getAllPlatforms } from '@/api/games'
+import { Plus } from '@element-plus/icons-vue'
+import type { UploadFile } from 'element-plus'
 
 const props = defineProps<{
   modelValue: boolean
@@ -23,10 +25,23 @@ const visible = computed({
 const name = ref('')
 const platform = ref<GamePlatform | ''>('')
 const tagsInput = ref('')
-const cover = ref('')
+const coverFile = ref<File | null>(null)
+const coverPreview = ref('')
 const loading = ref(false)
 const platforms = getAllPlatforms()
 
+function handleFileChange(uploadFile: UploadFile) {
+  if (uploadFile.raw) {
+    coverFile.value = uploadFile.raw
+    coverPreview.value = URL.createObjectURL(uploadFile.raw)
+  }
+}
+
+function handleFileRemove() {
+  coverFile.value = null
+  coverPreview.value = ''
+}
+
 async function handleSubmit() {
   if (!name.value.trim()) {
     ElMessage.warning('请输入游戏名称')
@@ -39,13 +54,14 @@ async function handleSubmit() {
       name: name.value.trim(),
       platform: platform.value || undefined,
       tags: tags.length > 0 ? tags : undefined,
-      cover: cover.value.trim() || undefined
+      coverFile: coverFile.value || undefined
     })
     ElMessage.success('添加成功')
     name.value = ''
     platform.value = ''
     tagsInput.value = ''
-    cover.value = ''
+    coverFile.value = null
+    coverPreview.value = ''
     emit('created')
     visible.value = false
   } catch (error: any) {
@@ -74,8 +90,23 @@ async function handleSubmit() {
         <el-input v-model="tagsInput" placeholder="逗号分隔，如: MOBA,竞技,5v5" />
       </div>
       <div class="field">
-        <label>封面图 URL</label>
-        <el-input v-model="cover" placeholder="https://example.com/cover.jpg" />
+        <label>封面图</label>
+        <el-upload
+          :auto-upload="false"
+          :limit="1"
+          accept="image/*"
+          :on-change="handleFileChange"
+          :on-remove="handleFileRemove"
+          drag
+        >
+          <div v-if="coverPreview" class="cover-preview">
+            <img :src="coverPreview" alt="封面预览" />
+          </div>
+          <div v-else class="upload-placeholder">
+            <el-icon :size="28"><Plus /></el-icon>
+            <span>点击或拖拽上传封面</span>
+          </div>
+        </el-upload>
       </div>
     </div>
     <template #footer>
@@ -89,4 +120,19 @@ async function handleSubmit() {
 .form-fields { display: flex; flex-direction: column; gap: 18px; }
 .field { display: flex; flex-direction: column; gap: 6px; }
 .field label { font-size: 13px; font-weight: 500; color: var(--gg-text-secondary); }
+.cover-preview img {
+  width: 100%;
+  max-height: 200px;
+  object-fit: contain;
+  border-radius: 6px;
+}
+.upload-placeholder {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 8px;
+  padding: 20px;
+  color: var(--gg-text-muted);
+  font-size: 13px;
+}
 </style>

frontend/src/components/game/GameDetailDialog.vue

@@ -1,7 +1,7 @@
 <script setup lang="ts">
 import { computed, ref, onMounted } from 'vue'
 import type { Game } from '@/types'
-import { toggleFavorite, isFavorite, deleteGame } from '@/api/games'
+import { toggleFavorite, isFavorite, deleteGame, getGameCoverUrl } from '@/api/games'
 import { ElMessage, ElMessageBox } from 'element-plus'
 import { TrendCharts, StarFilled, Star, Delete } from '@element-plus/icons-vue'
 import GameComments from './GameComments.vue'
@@ -62,7 +62,7 @@ function handleCreateTeam() {
     <template v-if="game">
       <div class="game-detail">
         <div class="detail-cover-wrap">
-          <img :src="game.cover || '/game-placeholder.svg'" :alt="game.name" class="detail-cover" />
+          <img :src="getGameCoverUrl(game) || '/game-placeholder.svg'" :alt="game.name" class="detail-cover" />
         </div>
 
         <h2 class="detail-name">{{ game.name }}</h2>