feat(qsl): copy a card design from another profile

A second profile is usually the same operator with a different rig or a
different locator — same callsign, same cards. Having to redraw a design
because the antenna changed is work nobody should do.

The designer now lists the designs the active profile cannot see and copies a
chosen one into it. Designs it already sees — its own, and the shared ones —
are left out: they are not something to copy.

A COPY, not a move or a share. The original profile keeps its design untouched
and the duplicate is free to diverge, which it usually will: a second profile
exists because something differs, and that something often ends up on the card.

The PICTURES are copied too, and that is the part worth getting right. Stored
documents reference photos by name relative to the template's own asset folder,
so duplicating the JSON alone would point the new design at files that are not
in its folder. It is validated against its own folder afterwards, and a failure
rolls the row back rather than leaving a design whose pictures are missing.
Sharing the source's folder was the other option and a worse one: deleting
either design would then have emptied the other.

changelog.json

@@ -5,12 +5,14 @@
     "en": [
       "Amplifiers: tick the ones sharing a combiner and ON, OFF and OPERATE act on all of them at once. Each keeps its own meters.",
       "Shared CAT: with the wire trace on, every command a client sends and the answer given are logged.",
-      "Shared CAT: JTDX and WSJT-X no longer get an error for turning split off on a rig that has none, or for setting the transmit mode — which made JTDX abandon a transmission."
+      "Shared CAT: JTDX and WSJT-X no longer get an error for turning split off on a rig that has none, or for setting the transmit mode — which made JTDX abandon a transmission.",
+      "QSL designer: a card design can be copied from another profile, pictures included — a second profile for a different rig no longer means redrawing it."
     ],
     "fr": [
       "Amplificateurs : coche ceux qui partagent un combiner et ON, OFF et OPERATE agissent sur tous à la fois. Chacun garde ses mesures.",
       "CAT partagé : avec la trace activée, chaque commande envoyée par un client et la réponse donnée sont journalisées.",
-      "CAT partagé : JTDX et WSJT-X ne reçoivent plus d erreur en désactivant un split inexistant ni en réglant le mode d émission — ce qui faisait abandonner une émission à JTDX."
+      "CAT partagé : JTDX et WSJT-X ne reçoivent plus d erreur en désactivant un split inexistant ni en réglant le mode d émission — ce qui faisait abandonner une émission à JTDX.",
+      "Concepteur QSL : un modèle de carte peut être copié depuis un autre profil, images comprises — un second profil pour une autre radio n oblige plus à le redessiner."
     ]
   },
   {