feat: MSC4260 Report User, Bug #6 mutual exclusion, TDS toast compliance

- Add ReportUserModal.tsx — category dropdown + reason input, calls
  POST /_matrix/client/v3/users/{userId}/report via mx.http.authedRequest,
  inline success/error feedback, auto-closes 1500ms after success
- Wire Report User button into UserRoomProfile.tsx between UserModeration
  and UserDeviceSessions (hidden for own profile)
- Bug #6: enforce mutual exclusion between chat backgrounds and seasonal
  themes — ChatBgGrid clears seasonal→'off' on non-'none' pick;
  SeasonalBgGrid clears chatBackground→'none' on real theme pick;
  SeasonalEffect guards against legacy persisted state at render time
- TDS: strip all hardcoded hex/rgba fallbacks from LotusToastContainer.tsx
  (var(--lt-bg-card), --lt-accent-orange, --lt-text-primary/secondary,
  --lt-accent-orange-dim/border, --lt-box-glow-orange)
- Mark Bug #6 FIXED, MSC4260 DONE, toast TDS FIXED in LOTUS_BUGS.md and
  LOTUS_TODO.md; note EventReaders + CallControls already compliant

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/components/seasonal/SeasonalEffect.tsx

@@ -797,5 +797,9 @@ export function SeasonalEffect() {
   }, [settings.seasonalThemeOverride]);
 
   if (!theme) return null;
+  // Suppress seasonal overlay when a chat background is active — both running simultaneously
+  // wastes GPU and looks cluttered. The settings UI enforces mutual exclusion on write;
+  // this guard covers any legacy state already persisted.
+  if (settings.chatBackground !== 'none') return null;
   return <SeasonalOverlay theme={theme} reduced={reduced} />;
 }

src/app/components/user-profile/UserRoomProfile.tsx

@@ -28,6 +28,7 @@ import { Membership } from '../../../types/matrix/room';
 import { useRoomCreators } from '../../hooks/useRoomCreators';
 import { useRoomPermissions } from '../../hooks/useRoomPermissions';
 import { useMemberPowerCompare } from '../../hooks/useMemberPowerCompare';
+import { ReportUserModal } from '../../features/room/ReportUserModal';
 import { CreatorChip } from './CreatorChip';
 import { getDirectCreatePath, withSearchParam } from '../../pages/pathUtils';
 import { DirectCreateSearchParams } from '../../pages/paths';
@@ -272,6 +273,7 @@ type UserRoomProfileProps = {
 };
 export function UserRoomProfile({ userId }: UserRoomProfileProps) {
   const mx = useMatrixClient();
+  const [reportUserOpen, setReportUserOpen] = useState(false);
   const crossSigningActive = useCrossSigningActive();
   const useAuthentication = useMediaAuthentication();
   const navigate = useNavigate();
@@ -390,8 +392,25 @@ export function UserRoomProfile({ userId }: UserRoomProfileProps) {
           canKick={canKickUser && membership === Membership.Join}
           canBan={canBanUser && membership !== Membership.Ban}
         />
+        {userId !== myUserId && (
+          <Box style={{ padding: `0 ${config.space.S400} ${config.space.S200}` }}>
+            <Button
+              variant="Critical"
+              fill="None"
+              size="300"
+              radii="300"
+              before={<Icon size="50" src={Icons.Warning} />}
+              onClick={() => setReportUserOpen(true)}
+            >
+              <Text size="B300">Report User</Text>
+            </Button>
+          </Box>
+        )}
         {showEncryption && userId !== myUserId && <UserDeviceSessions userId={userId} />}
         {userId !== myUserId && <UserPrivateNotes userId={userId} />}
+        {reportUserOpen && (
+          <ReportUserModal userId={userId} onClose={() => setReportUserOpen(false)} />
+        )}
       </Box>
     </Box>
   );