[docs](trx-rs): write down how a contest and a confirmation are worked

The manual gains the contest exchange, the Cabrillo entry and the
confirmations.  The plan marks all five phases done, corrects the API paths
to the /api/logbook they were built under -- /logbook is the page, and the
bookmarks API already shadows its own page that way -- and records the two
decisions phase 5 settled: that the Cabrillo header comes from the operator
because no log can derive it, and that a confirmation counts from whichever
bureau answered.

The plan itself travels with this branch: it was written on a branch of its
own that was never proposed for merge, and the earlier attempts to update it
from the implementation branches were silent no-ops, because the edits did
not assert that they had found what they were replacing.

Refs #54

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SyX26FCpMQxiBoC7r5K1A7
Signed-off-by: Stan Grams <sjg@haxx.space>

docs/User-Manual.md

@@ -519,6 +519,30 @@ most the contact being written. It lives in your data directory by default;
 `[trx-client.logbook].path` moves it, for a station that keeps its log on a
 backed-up volume.
 
+### Contests
+
+The **Contest exchange** block on the entry holds the contest's name and the
+serials — sent and received. Both stay between contacts, because they belong to
+the session rather than to the contact just logged, and the serial sent counts
+on by itself so it is not retyped forty times an hour. An exchange that is a
+zone, a section or a name rather than a number is kept as written.
+
+**Contest entry (Cabrillo)** exports the entry sponsors accept. Only the
+contacts of the contest named there are included. The header — operator
+category, power, claimed score — cannot be worked out from a log, so it is
+yours to fill in; the defaults are single operator, low power, all bands, mixed
+mode.
+
+### Confirmations
+
+The **QSL** column shows a tick when the other station has confirmed, and the
+**Confirm** button on a row records a card that has arrived. A confirmation
+counts from wherever it came: a paper card, LoTW or eQSL. An award wants one of
+them, not all three, so the log does not ask for all three.
+
+**Bands worked** counts, per band, the contacts made, the distinct stations
+worked, and how many of those contacts are confirmed.
+
 ### Ham radio layout
 
 The **Ham radio** operator layout opens on the logbook with the transceiver