[feat](trx-frontend-http): color VFOs and rework header title

Assign green to VFO A, yellow to VFO B, and deterministic hues
to additional VFOs. The active VFO color is also applied to the
main frequency display. Rework the header title to show
"trx-rs <version> @ <callsign>'s <rig>" instead of "<rig> status".

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Stanislaw Grams <stanislawgrams@gmail.com>

src/trx-client/trx-frontend/trx-frontend-http/assets/web/style.css

@@ -119,7 +119,6 @@ input.status-input, select.status-input { width: 100%; padding: 0.45rem 0.5rem;
 .vfo-picker button:last-child { border-right: none; }
 .vfo-picker button.active {
   background: var(--btn-bg);
-  color: var(--accent-green);
   font-weight: 600;
 }
 .signal-measure {