feat(stats): voice-time and message leaderboards per space

Voice stays get their own table rather than joining the audit log: that table
records points in time, a call is an interval, and pairing join/leave point
events would leave every query guessing at joins whose leave never arrived.

Sessions are opened and closed inside joinRoom/leaveCurrentRoom rather than at
the seven call sites that reach them, so no path can be missed, and
destroyRoom closes them too — it bypasses leaveCurrentRoom and would otherwise
leak open rows.

A restart leaves sessions open with an unknowable end time. They are closed at
startedAt, discarding that time rather than inventing it: crediting the gap
would hand someone hours they never spent, and the numbers are the point.
Mirrors the existing users.status sweep on boot.

Only closed sessions count, so a figure does not move on every refresh. Bars
scale to the leader, not the total — with five people every share of a total
looks identical. Statistics are readable by any member, since they are the
group's own numbers; the audit log, which names who did what, stays on
MANAGE_SPACE.

packages/web/src/components/modals/SpaceSettings.tsx

@@ -8,6 +8,7 @@ import { api } from '../../api/client';
 import { hasPermissionBit, PermissionBits } from '../../utils/permissions';
 import { OverviewPanel } from './spaceSettingsPanels/OverviewPanel';
 import { AuditLogPanel } from './spaceSettingsPanels/AuditLogPanel';
+import { StatsPanel } from './spaceSettingsPanels/StatsPanel';
 import { useT } from '../../i18n';
 import { MembersPanel } from './spaceSettingsPanels/MembersPanel';
 import { RolesPanel } from './spaceSettingsPanels/RolesPanel';
@@ -269,7 +270,7 @@ export function SpaceSettingsModal() {
   const spacePermissions = useSpaceStore((s) => s.spacePermissions);
 
   const t = useT();
-  const [tab, setTab] = useState<'overview' | 'discovery' | 'members' | 'roles' | 'bans' | 'audit'>('overview');
+  const [tab, setTab] = useState<'overview' | 'discovery' | 'members' | 'roles' | 'bans' | 'audit' | 'stats'>('overview');
   const [mobileView, setMobileView] = useState<'tabs' | 'content'>('tabs');
 
   const isOpen = activeModal === 'spaceSettings';
@@ -337,6 +338,7 @@ export function SpaceSettingsModal() {
             {canManageSpace && (
               <button onClick={() => handleTabClick('audit')} className={tabClass('audit')}>{t('audit.title')}</button>
             )}
+            <button onClick={() => handleTabClick('stats')} className={tabClass('stats')}>{t('stats.title')}</button>
           </div>
         </div>
 
@@ -375,6 +377,7 @@ export function SpaceSettingsModal() {
               {canManageSpace && (
                 <button onClick={() => handleTabClick('audit')} className={tabClass('audit')}>{t('audit.title')}</button>
               )}
+              <button onClick={() => handleTabClick('stats')} className={tabClass('stats')}>{t('stats.title')}</button>
             </div>
           </div>
         )}
@@ -402,6 +405,7 @@ export function SpaceSettingsModal() {
               {tab === 'roles' && canManageRoles && <RolesPanel spaceId={currentSpaceId} />}
               {tab === 'bans' && canBanMembers && <BansPanel spaceId={currentSpaceId} />}
               {tab === 'audit' && canManageSpace && <AuditLogPanel spaceId={currentSpaceId} />}
+              {tab === 'stats' && <StatsPanel spaceId={currentSpaceId} />}
             </div>
           </div>
         )}