feat(frontend): chat tabs, flat SVG icons, upload autosave, per-user rights

- Chat rework: Chats (private DMs with user search, online dots, unread
  badges) and Team chats tabs; shared message component with reactions,
  edit, image attachments, message search and typing indicators
- Flat modern inline SVG icon set (no external dependency) replaces
  emoji chrome across nav, headers, buttons, tabs and settings
- Uploaded avatar/background images apply instantly (auto-save) with
  confirmation note; per-user permission matrix in dashboard members
- Login localized, invite header uses icon, comment header cleaned

frontend/src/components/Bell.vue

@@ -5,6 +5,7 @@ import api from '../api';
 import { getSocket } from '../socket';
 import { useLocaleStore } from '../stores/locale';
 import { useWorkspaceStore } from '../stores/workspace';
+import Icon from './Icon.vue';
 
 const L = useLocaleStore();
 const ws = useWorkspaceStore();
@@ -75,10 +76,10 @@ onUnmounted(() => {
 <template>
   <div class="bell">
     <button class="ghost icon-btn bell-btn" @click="open = !open" :title="L.t('bell.title')">
-      🔔<span v-if="total" class="badge">{{ total }}</span>
+      <Icon name="bell" /><span v-if="total" class="badge">{{ total }}</span>
     </button>
     <div v-if="open" class="card bell-pop">
-      <h4 style="margin: 0 0 8px">🔔 {{ L.t('bell.title') }}</h4>
+      <h4 style="margin: 0 0 8px"><Icon name="bell" :size="16" /> {{ L.t('bell.title') }}</h4>
       <div v-if="invites.length">
         <div class="side-label">{{ L.t('bell.invites') }}</div>
         <div v-for="inv in invites" :key="inv.id" class="card invite-card">