Audio cues: add send/receive on-off and minimise/restore cues (2 sounds each), drop .sfk byproducts

Six new machine-wide cues, each with the same numbered-variant + Preferences treatment as
the others (enable tickbox, Choose default sound picker, Play/Browse):

- Send turned on / off, Receive turned on / off: fire from OnStreamingCheckboxChanged, so
  they sound whether the user clicked the in-window tickbox or pressed the mute shortcut
  (the hotkey flips .Checked, which routes through the same handler). Suppressed during
  profile load by the existing password-gate guard, so loading a profile doesn't blast them.
- Minimise (hide) / Restore (show): fire from the tray controller's Minimize()/Restore() on a
  genuine visibility transition (guarded against no-op / startup-minimise).

Enable flags + custom-WAV overrides for these six live machine-wide in AppConfig
(EnableSendOnCue.., MachineCueCustomPaths) - they're app-level feedback, not per-profile
audio - so no Profile/settings-cache plumbing. TryLoadCueSound now also honours the
machine-wide custom path. PreferencesDialog gains a MachineRow helper + the six rows.

Sounds: shipped via the existing sounds\*.wav wildcard. Fixed an obvious typo in the
supplied files ("rcieve off 1.wav" -> "recieve off 1.wav") so receive-off has both variants.
Renamed the old single-name cue WAVs to Ed's numbered-variant set; added key/passkey and the
new cue sounds.

build-release.ps1: new step deletes the SoundForge .sfk peak-file byproducts from sounds\
before packaging (they never shipped - build is *.wav only - this just keeps the tree tidy).

Tests + manual updated for the six new cues.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

run-tests.ps1

@@ -48,7 +48,7 @@ $soundsPath = Join-Path $publishDir 'sounds'
 $wavCount = @(Get-ChildItem -LiteralPath $soundsPath -Filter *.wav -ErrorAction SilentlyContinue).Count
 if ($wavCount -ge 3) { Pass "cue sounds bundled ($wavCount .wav)" } else { Fail "cue sounds missing (found $wavCount) - this is the bug that shipped v3.9 with no sounds" }
 # Cues ship as numbered variants ("connect 1.wav", ...); each required cue needs at least one.
-foreach ($base in @('connect', 'disconnect', 'start up')) {
+foreach ($base in @('connect', 'disconnect', 'start up', 'send on', 'send off', 'recieve on', 'recieve off', 'minimise', 'maximise')) {
     $variants = @(Get-ChildItem -LiteralPath $soundsPath -Filter "$base*.wav" -ErrorAction SilentlyContinue)
     if ($variants.Count -gt 0) { Pass "'$base' cue has $($variants.Count) sound variant(s)" } else { Fail "no sound variant for the '$base' cue" }
 }