feat(awards): an entity that IS one island group fills its own IOTA reference

QRZ carries <iota> only for the operators who filled it in, and most have not.
But for 99 entities the reference follows from the entity alone — a station in
Ascension is on AF-003 whatever its callbook record says — and the entity is
known for every callsign from cty.dat, with no callbook at all.

So this reaches the operator with no QRZ subscription and the station that has
never touched a callbook, and it lands before the contact is logged, which is
when a reference is worth having.

Filled ONLY when the callbook gave nothing: an operator who typed a reference
knows something a table cannot — an IOTA-heavy entity, a rare island being
activated — and that still wins, as does one picked by hand on the entry.

The table is the IOTA programme's own dxcc_matches_one_iota.json, which lists
exactly the entities that map to ONE reference. France is not among them: a
French station is usually on the mainland and on no island, and guessing would
put a reference on hundreds of contacts that earn none.

Held as a table rather than a download — 3.5 kB that changes when an entity
appears, so fetching it daily would buy nothing and would fail exactly where a
portable station usually is. The header says where it came from and how to
refresh it.

Follows 747c2b9 and eab11db, which read the callbook's own tag.

changelog.json

@@ -2,8 +2,12 @@
   {
     "version": "0.25.8",
     "date": "",
-    "en": [],
-    "fr": []
+    "en": [
+      "An entity that is a single island group now fills the IOTA reference on its own — no callbook subscription needed."
+    ],
+    "fr": [
+      "Une entité qui est un seul groupe d’îles remplit désormais la référence IOTA toute seule, sans abonnement callbook."
+    ]
   },
   {
     "version": "0.25.7",