fix: bug fixes and UX improvements (v0.3.5)

- Fix clipboard copy error in HTTP environment with execCommand fallback
- Fix team invite page not loading user groups, always showing "join group first"
- Fix JoinGroupPage isMember check using group object instead of user ID
- Fix cancelRSVP deleting all users' RSVP records instead of current user's
- Fix event detail not loading event data itself
- Fix event comment avatar URL missing PocketBase baseUrl prefix
- Fix event creation missing endTime > startTime validation
- Fix event manage/delete permission split (creator+owner vs creator+owner)
- Fix event create button only visible to admins, now all members can create
- Fix event expand not subscribing to comments/RSVP realtime updates
- Fix event relative time not using status field
- Remove duplicate create/join group buttons from header and welcome bar
- Refactor team invite link to use API function

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

frontend/src/views/Home.vue

@@ -78,14 +78,6 @@ function openGameDetail(game: Game) {
           <span v-if="userStore.user?.statusNote" class="status-note">{{ userStore.user.statusNote }}</span>
         </div>
       </div>
-      <div v-if="!hasNoGroup" class="welcome-actions">
-        <button class="cta-btn cta-btn--primary" @click="showCreateGroup = true">
-          <el-icon><Plus /></el-icon> 创建群组
-        </button>
-        <button class="cta-btn cta-btn--secondary" @click="showJoinGroup = true">
-          <el-icon><Search /></el-icon> 加入群组
-        </button>
-      </div>
     </section>
 
     <!-- 无群组引导 -->