fix/polish: wave 1+2 improvements across six features

B1 - GIF upload progress: spinner on GIF button + disabled state while
     fetch+upload is in flight; clears on success or error
B2 - PiP position persistence: drag end saves left/top to localStorage;
     entering PiP restores saved position (clamped to current viewport)
B3 - PiP snap-to-corner: double-click the PiP overlay snaps to nearest
     corner with a 180ms CSS transition; saves new position
B4 - Device sessions loading state: useOtherUserDevices now returns
     {status:'loading'|'error'|'success', devices} instead of bare
     array; UserDeviceSessions shows spinner while loading
B5 - Device sessions error state: catch in hook sets status:'error';
     panel shows warning icon + 'Could not load sessions' message
B6 - Screenshare fullscreen Safari guard: hide button when
     document.fullscreenEnabled is false (iOS Safari, some mobile)
B7 - Status save error: show critical-coloured error text below Save
     button when saveState.status === AsyncStatus.Error
B9 - Encrypted search coverage counter: 'X / Y cached' badge next to
     'Encrypted Rooms' heading using existing localResult fields
D2 - PiP screenshare spotlight: track auto-spotlight in a ref; release
     spotlight when screenshare ends while in PiP mode

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

src/app/features/message-search/MessageSearch.tsx

@@ -508,6 +508,9 @@ export function MessageSearch({
             <Box alignItems="Center" gap="200">
               <Icon size="200" src={Icons.Lock} />
               <Text size="H5">Encrypted Rooms</Text>
+              <Text size="T200" style={{ opacity: 0.55 }}>
+                {`${localResult.searchedRoomsCount} / ${localResult.encryptedRoomsCount} cached`}
+              </Text>
             </Box>
             <Text size="T300" priority="300">
               {localResult.groups.length > 0