feat(bandmap): draw the band plan of the operator's IARU region

The band maps carried one hard-coded table — Region 1's — so a US operator's
40 m stopped at 7200 with stations spotted at 7250 hanging past the top of the
map, and the SSB wash started 25 kHz early. The region is a station-level fact
stated once (Settings → General, portable pref); lib/bandplan owns the three
tables and publishes changes to the open maps the way the distance unit reaches
the grids.

The tables stay deliberately coarse: a band map's wash is context, not a
regulatory chart, so only the differences an operator notices are split out —
Region 2's 80 m to 4000 and 40 m to 7300 (phone from 7125), Region 3's 80 m to
3900, the wider VHF/UHF allocations. National fine print does not belong in a
background tint.

frontend/src/lib/uiPref.ts

@@ -41,6 +41,7 @@ const PORTABLE_KEYS = [
   'opslog.clusterLockBand', 'opslog.clusterLockMode', 'opslog.clusterStatusFilter',
   'opslog.clusterModeFilter', 'opslog.clusterSearch', 'opslog.clusterHideWorked',
   'opslog.distanceMiles', // distances shown in statute miles rather than km
+  'opslog.iaruRegion',    // IARU region (1/2/3) — band edges and segments on the band maps
   'opslog.activeTab',     // last selected tab
   'opslog.mainSplit',    // Main tab: width share of the left pane (percent) — legacy, read once to seed mainShares
   'opslog.mainShares',   // Main tab: column shares per column count, as {2:[..],3:[..],4:[..]}