fix(relays): the generic HTTP board never sent its URLs; cluster filters start off

buildDeviceDriver had no case for "httpgen", so the generic board fell through
to the WebSwitch driver: it polled an address it had never been given, reported
itself offline, greyed out every relay button, and sent none of the configured
URLs. Nothing in the interface said so — the board was configured, saved and
listed, and simply did nothing. deviceKey did not cover the URLs either, so once
that is fixed, correcting a typo in one would still have handed back the cached
driver holding the old address until a restart.

Two shapes of home-made switch could not be described at all:

  - a bit-mask board whose four URLs differ by one character
    (/Set0/1, /Set0/2, /Set0/4, /Set0/8) — {value} in the pattern now takes the
    number from the per-relay box, keeping the address in one place;
  - a board numbering its channels from zero — {relay-1}, since giving up the
    pattern for eight hand-typed URLs was the only alternative.

The pattern decides what the per-relay boxes hold, and the grid says which as
soon as {value} is typed: guessing per box ("does this look like a URL?") would
change meaning on a typo, which is not a thing to do to something wired to an
antenna. A URL typed without a scheme gets http:// like the named boards get
from relayBase; https:// is passed through untouched.

Host and the connection test are gone for this type. It has no address of its
own — its relays may each live on a different box — and no status to read, so a
test could only ever answer "OK, 4 relays". Save was greyed out without a host,
which made a complete configuration of four full URLs impossible to store.

Cluster filters no longer persist across launches. A band lock set weeks earlier
is invisible to whoever set it: the counter reads 76 spots live, the grid is
empty, and the search goes to the cluster instead. Nobody loses work by
re-ticking a chip. Grouping and the panel state still persist — they change how
spots look, never whether they appear.

frontend/src/lib/uiPref.ts

@@ -34,10 +34,12 @@ 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
-  // 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.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.
   '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