revert(cluster): keep the filter selections across restarts

They were made session-only on a misreading: the ask was about the FIRST launch
of a fresh install, not every launch. Restored as they were — restored on
reopen, and travelling with a copied data/ folder.

A first-ever launch already starts with nothing filtered: every selection
defaults to empty or off and there is no code that switches one on. The one
route by which a new installation can come up filtered is a copied data/ folder,
which carries the previous machine's selections by design.

The filtered-out message and the clear-every-filter button stay: they are what
makes a filter that IS set visible, whenever it was set.

frontend/src/lib/uiPref.ts

@@ -34,12 +34,10 @@ const PORTABLE_KEYS = [
   'opslog.dateFormat',    // how dates are DISPLAYED (iso / fr / us); storage stays ISO
   'opslog.mapGreyline',   // world map: grey line (day/night terminator) shown
   'opslog.awardRefSort', 'opslog.awardRefSortDir', // award reference table: sort column and direction
-  'opslog.clusterGroup',  // cluster: group spots by callsign
-  // NOTE: the cluster FILTERS (band, mode, the two rig locks, status, search,
-  // LoTW-only, spotter continent, source) are deliberately absent. They start
-  // off at every launch — a filter restored from a previous session is invisible
-  // to whoever set it, and an empty spot list beside a live counter reads as a
-  // broken cluster. See the comment on their state in App.tsx.
+  // Cluster filter selections — restored on reopen.
+  'opslog.clusterFilterSource', 'opslog.clusterGroup', 'opslog.clusterBands',
+  'opslog.clusterLockBand', 'opslog.clusterLockMode', 'opslog.clusterStatusFilter',
+  'opslog.clusterModeFilter', 'opslog.clusterSearch', 'opslog.clusterHideWorked',
   'opslog.activeTab',     // last selected tab
   'opslog.mainSplit',    // Main tab: width share of the left pane (percent)
   'opslog.clusterMuteWorked',    // cluster/band map: no colour or badge on worked spots