[feat](trx-client): merge R/T hotkeys into single R, add F for freq input

Combine round (R) and retune (T) into a single R hotkey that rounds to
the nearest jog step boundary, or retunes if already rounded. Update F
hotkey description to "Pick frequency" in the F1 help overlay.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-client/trx-frontend/trx-frontend-http/assets/web/index.html

@@ -1347,9 +1347,8 @@
       <div class="shortcut-overlay-title">Keyboard Shortcuts</div>
       <table class="shortcut-table">
         <tbody>
-          <tr><td class="shortcut-key"><kbd>F</kbd></td><td>Focus frequency input</td></tr>
-          <tr><td class="shortcut-key"><kbd>R</kbd></td><td>Round frequency up to next step</td></tr>
-          <tr><td class="shortcut-key"><kbd>T</kbd></td><td>Retune current frequency</td></tr>
+          <tr><td class="shortcut-key"><kbd>F</kbd></td><td>Pick frequency (focus input)</td></tr>
+          <tr><td class="shortcut-key"><kbd>R</kbd></td><td>Round to nearest step / retune</td></tr>
           <tr><td class="shortcut-key"><kbd>B</kbd></td><td>Jump to previous freq/bw/mode</td></tr>
           <tr><td class="shortcut-key"><kbd>[</kbd> / <kbd>]</kbd></td><td>Narrow / widen bandwidth (±10 kHz)</td></tr>
           <tr><td class="shortcut-key"><kbd>←</kbd> / <kbd>→</kbd></td><td>Tune by current step</td></tr>