Fix non-portable ADIF export fields and surface upload failure reasons

[patrickrb]

Found while diagnosing why every QSO upload to a Cloudlog-compatible server had
been failing silently for three days. The server-side cause was its own
problem, but getting there surfaced three real app-side ones.

Zero-length fields make records unimportable

An optional value that was present-but-empty exported as <gridsquare:0> .
Several ADIF importers treat a length-0 field as malformed and reject the whole
record instead of reading it as "absent" — 39 of 384 records in a real export
carried one, from QSOs where the other station never sent a grid.

Empty now means omitted, which every parser agrees on.

Two follow-ons the new tests caught:

• mode had its own null-only guard (it branches separately for the MFSK
  submode split) and so kept emitting <mode:0> after the shared helper was
  fixed.
• comment was emitted unconditionally because the <eor> terminator was
  glued onto it. They are separate now, so a commentless QSO no longer carries
  a zero-length comment purely to hold the terminator.

QSL_MANUAL is not an ADIF field

The bare name is non-conformant — ADIF reserves APP_<PROGRAMID>_ for
program-specific data, precisely so consumers can skip what they don't know
instead of erroring on it.

We now write APP_FT8AF_QSL_MANUAL. QSLRecord reads both names, so ADIF
files written by older FT8AF builds keep importing with their confirmation flag
intact.

Upload failures were invisible

uploadAdifToCloudlog returned a bare boolean, and the server's own
explanation went only to Log.d. So debug.log recorded:

QsoAutoSync: done (app-start): cloudlog=0 qrz=0 of 113

…which reads identically whether the network was down, the API key expired, or
the server was rejecting every single record. The backlog grew from 74 to 113
QSOs across three days with nothing to point at.

The reason now flows through SyncResult into that line:

QsoAutoSync: done (app-start): cloudlog=0 qrz=0 of 113
  cloudlogError=HTTP 400: {"status":"abort","adif_errors":1,"messages":
  ["column \"tx_pwr\" of relation \"contacts\" does not exist"]}

That is a 30-second diagnosis. The description is collapsed to one line and
truncated (a misconfigured proxy can return a whole HTML error page), and the
QRZ variant deliberately reports only RESULT/REASON — the rest of QRZ's
response echoes the submitted ADIF back, which has no business accumulating in
debug.log.

Also: one ADIF builder instead of two

DatabaseOpr.downQSLTable — the built-in web logbook's ADIF download — was a
line-for-line duplicate of AdifRecord.build(), same fields in the same order.
The copies had drifted: it still carried both bugs above long after the
file-export path was fixed. It now maps its cursor onto AdifRecord and
nothing else (-95 lines), so the next formatting fix can't land in only one of
them. Its existing tests cover the mapping, plus new ones for the empty-value
and field-name behaviour.

Testing

testDebugUnitTest: 2881 pass. New coverage for zero-length omission across
every optional field, the APP_ prefix and legacy-name import round-trip, and
the failure-reason formatting (status + body, newline collapsing, truncation,
and never echoing submitted ADIF).

Built and installed on a Pixel 8. The device disconnected before the
debug.log line could be observed in the wild, so that last confirmation is
still outstanding — the log format itself is unit-tested.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 36.72%. Comparing base (0360375) to head (8050f6d).

Files with missing lines	Patch %	Lines
...main/kotlin/radio/ks3ckc/ft8af/sync/QsoAutoSync.kt	83.33%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                dev     #701      +/-   ##
============================================
+ Coverage     36.70%   36.72%   +0.01%     
  Complexity      222      222              
============================================
  Files           227      227              
  Lines         27933    27938       +5     
  Branches       3485     3487       +2     
============================================
+ Hits          10254    10259       +5     
  Misses        17426    17426              
  Partials        253      253              

Flag	Coverage Δ
android	16.39% <83.33%> (+0.02%)	⬆️
native	9.93% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...main/kotlin/radio/ks3ckc/ft8af/sync/QsoAutoSync.kt	21.87% <83.33%> (+6.62%)	⬆️

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