[fix](trx-frontend-http): gate APRS bar to PKT mode, reject CRC failures

- Hide bar whenever mode != PKT; app.js calls window.updateAprsBar()
  on every server-pushed mode change so the bar disappears immediately
- CRC-failed frames are excluded from the bar (both live and history
  restore); the [CRC] rendering path is removed
- Offset bar 1.2 rem from left edge for visual breathing room

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-client/trx-frontend/trx-frontend-http/assets/web/app.js

@@ -1419,6 +1419,7 @@ function render(update) {
   if (aprsStatus && modeUpper !== "PKT" && aprsStatus.textContent === "Receiving") {
     aprsStatus.textContent = "Connected, listening for packets";
   }
+  if (window.updateAprsBar) window.updateAprsBar();
   if (cwStatus && modeUpper !== "CW" && modeUpper !== "CWR" && cwStatus.textContent === "Receiving") {
     cwStatus.textContent = "Connected, listening for packets";
   }