Add callsign/grid/band search to the Logbook Recent tab

[patrickrb]

What & why

The Logbook Recent tab listed every logged QSO with no way to search. Answering the everyday operator question — "have I worked this station before, and on what band?" — meant scrolling the entire log. This PR adds a search box above the recent list that filters the log as you type.

Users notice this immediately: tap Logbook → Recent, type a partial call, and the list narrows to matching contacts.

Behavior

• Case-insensitive substring match (so "PA" finds both PA3XYZ and W1PA) across the fields an operator actually searches a log by:
  • callsign (primary)
  • grid (e.g. FN42)
  • band (e.g. 40M)
  • DXCC entity (e.g. Japan)
  • stored location / "where"
• A blank query shows the full list (no filtering).
• A clear (✕) button resets the query.
• When records exist but nothing matches, a distinct "No matching QSOs" state is shown with the search box still in place, so the query can be refined or cleared.
• The query lives in a rememberSaveable, so it survives rotation/recomposition but resets when you leave the Logbook — matching the expectation that search is a transient "find this contact" action, not a persisted filter.

Design

Per the project convention (Composables can't be unit-tested directly), all match logic is extracted into a pure top-level internal fun filterQsoRecords(records, query); the search bar (LogSearchBar) is a thin Compose wrapper that just calls it. Sorting is unchanged — the filtered list still flows through the existing sortQsosByDateTimeDesc.

Tests

New LogbookSearchTest (pure JVM, no Robolectric) covering: blank/whitespace query passthrough, callsign prefix + mid-string substring, case-insensitivity, match by grid/band/DXCC/where, query trimming, no-match empty result, empty log, and null optional fields.

./gradlew :app:testDebugUnitTest --tests "radio.ks3ckc.ft8af.ui.logbook.*"  → BUILD SUCCESSFUL

:app:compileDebugKotlin also passes. No decoder/TX/protocol code touched.

Scope

Focused, additive, UI-only. Nothing outside the Recent tab changes.

[codecov]

Codecov Report

❌ Patch coverage is 12.82051% with 68 lines in your changes missing coverage. Please review.
✅ Project coverage is 36.71%. Comparing base (d5686e7) to head (106dd68).

Files with missing lines	Patch %	Lines
...lin/radio/ks3ckc/ft8af/ui/logbook/LogbookScreen.kt	12.82%	68 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                dev     #677      +/-   ##
============================================
- Coverage     36.73%   36.71%   -0.03%     
- Complexity      197      211      +14     
============================================
  Files           216      219       +3     
  Lines         26882    27168     +286     
  Branches       3284     3340      +56     
============================================
+ Hits           9876     9975      +99     
- Misses        16781    16957     +176     
- Partials        225      236      +11     

Flag	Coverage Δ
android	15.38% <12.82%> (+0.35%)	⬆️
native	9.93% <ø> (ø)

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Files with missing lines	Coverage Δ
...lin/radio/ks3ckc/ft8af/ui/logbook/LogbookScreen.kt	7.49% <12.82%> (+0.89%)	⬆️

... and 13 files with indirect coverage changes

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