Tap the card, and that is the whole enrolment

The reader already filled the number in; adding it still meant walking
back to the keyboard and pressing Add. That walk was the entire cost of
the two-step version, and the card is in your hand at the charger. One
press now opens the reader and writes whatever is held against it.

The name is the server's own convention — RFID and the card's last four
digits — because the name is left empty and rfidSaveCard fills it in.
Deriving the same pattern here would have been a second place for it to
drift; every card already on the account reads that way. A name typed
into the box still wins, since throwing away what somebody typed is
worse than the convention.

The reader is a value now rather than a side effect on the form, and the
write is shared with the typed path so the two cannot judge their answers
differently. The caller holds the busy flag across both halves: nothing
re-enables in the gap, where a second press would have opened a second
twenty-second window. The number lands in the box on the way past, so a
write that fails leaves something to retry rather than a card nobody can
name.

The old button stays for the times the number is wanted without the card
being added.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Web App/web/src/i18n/da.json

@@ -72,6 +72,8 @@
       "tap": "Hold kortet mod laderen",
       "tapping": "Hold kortet mod læseren… {n}s",
       "tapHint": "Læseren er åben. Hold kortet mod laderen.",
+      "tapSave": "Hold kortet mod laderen, og tilføj det",
+      "tapSaveHint": "Tilføjer kortet, så snart det holdes mod læseren, med navnet RFID og kortets sidste fire cifre.",
       "tapNone": "Der blev ikke holdt et kort mod læseren, før den lukkede.",
       "addTitle": "Tilføj et kort",
       "remove": "Fjern",