feat(station): MY_IOTA in the station profile

IOTA is an official ADIF field, and almost everything for it was already here:
the qso table has carried my_iota since the first migration, the insert and scan
handle it, and both ADIF import and export write it. The one missing link was
the station profile, so the reference had to be typed on every contact of an
island activation, or added afterwards in a bulk edit.

Migration 0025 adds the column; it joins my_sota_ref and my_pota_ref in the
profile, in the Station Information panel, and in the same stamp-if-empty block
that fills the other My* fields on a logged QSO.

Uppercased and trimmed on save. ADIF spells it EU-005, and an operator typing
"eu-005" would otherwise put a reference no award matcher recognises on every
QSO of an activation - the kind of mistake you only find months later.

internal/db/migrations/0025_profile_iota.sql

@@ -0,0 +1,7 @@
+-- MY_IOTA: the island reference the station operates FROM, e.g. "EU-005".
+--
+-- An official ADIF field, and the QSO table has carried my_iota since 0001 —
+-- only the station profile could not supply it, so an island activation had to
+-- have the reference typed on every contact or added afterwards. Blank by
+-- default: the overwhelming majority of stations are not on an island.
+ALTER TABLE station_profiles ADD COLUMN my_iota TEXT NOT NULL DEFAULT '';