feat(bandmap): drag the width, and remember it

Both band maps were pinned to a hardcoded width — 300px docked beside the
tables, 260px per card in the Band map tab. On a busy band the map could not be
given more room, and on a quiet one the log could not take it back.

The docked map becomes a resizable grid column with the grip in the gap between
the panes, so the handle costs no space; the tab cards share one width with the
grip on their right edge. Side-by-side columns of different widths read as a
mistake rather than a choice, which is why the tab has one width and not one
per card. Double-click either grip to return to the default.

The drag measures from the pointer's START position rather than the container,
so the same helper serves both edges — the docked map sits on the left or the
right depending on the operator's setting, and the grip is on its inner edge
either way. Pointer capture, like the main splitter: without it the map or the
grid under the cursor swallows the moves.

Both widths are persisted through writeUiPref and registered as portable, so
they travel with the data folder like the main splitter and the rest of the
layout.

frontend/src/lib/i18n.tsx

@@ -342,7 +342,7 @@ const en: Dict = {
   'bmp.statusNew': 'NEW DXCC (entity never worked)', 'bmp.statusNewBand': 'NEW BAND (entity not worked on this band)', 'bmp.statusNewSlot': 'NEW SLOT (mode not worked on this band)',
   'bmp.statusWorked': 'Worked (this band + mode already in log)', 'bmp.statusUnresolved': 'Entity not resolved', 'bmp.bandMap': 'Band map', 'bmp.notConfigured': 'Not configured for {band}.',
   'bmp.map': 'Map', 'bmp.zoomOut': 'Zoom out', 'bmp.zoomIn': 'Zoom in', 'bmp.scrollToRig': 'Scroll to current rig frequency', 'bmp.moveLeft': 'Move band map to the left', 'bmp.moveRight': 'Move band map to the right', 'bmp.hide': 'Hide band map',
-  'bmp.bandsLabel': 'Bands:', 'bmp.fit': 'FIT', 'bmp.hideFt': 'Hide FTx', 'bmp.hideFtTitle': 'Hide all digital (FT8/FT4/JS8/…) spots on every band map', 'bmp.fitBand': 'Fit to band', 'bmp.fitTitle': 'Size each band map to show the whole band edge-to-edge',
+  'bmp.bandsLabel': 'Bands:', 'bmp.fit': 'FIT', 'bmp.hideFt': 'Hide FTx', 'bmp.hideFtTitle': 'Hide all digital (FT8/FT4/JS8/…) spots on every band map', 'bmp.fitBand': 'Fit to band', 'bmp.widthTip': 'Drag to resize — double-click to reset', 'bmp.fitTitle': 'Size each band map to show the whole band edge-to-edge',
   'bmp.legendNewDxcc': 'New DXCC', 'bmp.legendNewBand': 'New band', 'bmp.legendNewSlot': 'New slot (mode)', 'bmp.legendWorked': 'Worked', 'bmp.legendCW': 'CW', 'bmp.legendData': 'Data', 'bmp.legendPhone': 'Phone', 'bmp.footerHint': 'scroll · ctrl+wheel = zoom · ◎ = jump to rig', 'bmp.spotsHidden': '{n} FT8/FT4 spots hidden — top {max} kept (CW/SSB all shown)',
   'frm.welcome': 'Welcome to OpsLog', 'frm.intro': 'Set up your station to start logging. These fields stamp every QSO and can be changed later in Preferences → Station Information (and per profile).',
   'frm.callsign': 'Callsign', 'frm.locator': 'Locator', 'frm.operator': 'Operator', 'frm.operatorPh': 'same as callsign', 'frm.owner': 'Owner', 'frm.ownerPh': 'station owner callsign', 'frm.name': 'Name', 'frm.namePh': 'your first name',
@@ -750,7 +750,7 @@ const fr: Dict = {
   'bmp.statusNew': 'NOUVEAU DXCC (entité jamais contactée)', 'bmp.statusNewBand': 'NOUVELLE BANDE (entité non contactée sur cette bande)', 'bmp.statusNewSlot': 'NOUVEAU MODE (mode non contacté sur cette bande)',
   'bmp.statusWorked': 'Contacté (cette bande + mode déjà au log)', 'bmp.statusUnresolved': 'Entité non résolue', 'bmp.bandMap': 'Carte de bande', 'bmp.notConfigured': 'Non configurée pour {band}.',
   'bmp.map': 'Carte', 'bmp.zoomOut': 'Dézoomer', 'bmp.zoomIn': 'Zoomer', 'bmp.scrollToRig': 'Aller à la fréquence actuelle du poste', 'bmp.moveLeft': 'Déplacer la carte de bande à gauche', 'bmp.moveRight': 'Déplacer la carte de bande à droite', 'bmp.hide': 'Masquer la carte de bande',
-  'bmp.bandsLabel': 'Bandes :', 'bmp.fit': 'FIT', 'bmp.hideFt': 'Masquer FTx', 'bmp.hideFtTitle': 'Masquer tous les spots numériques (FT8/FT4/JS8/…) sur toutes les cartes', 'bmp.fitBand': 'Ajuster à la bande', 'bmp.fitTitle': 'Dimensionner chaque carte pour afficher toute la bande',
+  'bmp.bandsLabel': 'Bandes :', 'bmp.fit': 'FIT', 'bmp.hideFt': 'Masquer FTx', 'bmp.hideFtTitle': 'Masquer tous les spots numériques (FT8/FT4/JS8/…) sur toutes les cartes', 'bmp.fitBand': 'Ajuster à la bande', 'bmp.widthTip': 'Glisser pour redimensionner — double-clic pour réinitialiser', 'bmp.fitTitle': 'Dimensionner chaque carte pour afficher toute la bande',
   'bmp.legendNewDxcc': 'Nouveau DXCC', 'bmp.legendNewBand': 'Nouvelle bande', 'bmp.legendNewSlot': 'Nouveau mode', 'bmp.legendWorked': 'Contacté', 'bmp.legendCW': 'CW', 'bmp.legendData': 'Numérique', 'bmp.legendPhone': 'Phonie', 'bmp.footerHint': 'défiler · ctrl+molette = zoom · ◎ = aller au poste', 'bmp.spotsHidden': '{n} spots FT8/FT4 masqués — {max} meilleurs conservés (CW/SSB tous affichés)',
   'frm.welcome': 'Bienvenue dans OpsLog', 'frm.intro': 'Configure ta station pour commencer à logger. Ces champs sont inscrits sur chaque QSO et peuvent être modifiés plus tard dans Préférences → Informations station (et par profil).',
   'frm.callsign': 'Indicatif', 'frm.locator': 'Locator', 'frm.operator': 'Opérateur', 'frm.operatorPh': "identique à l'indicatif", 'frm.owner': 'Propriétaire', 'frm.ownerPh': 'indicatif du propriétaire de la station', 'frm.name': 'Nom', 'frm.namePh': 'ton prénom',