[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/style.css

@@ -621,7 +621,7 @@ small { color: var(--text-muted); }
   display: none;
   position: absolute;
   bottom: 0.4rem;
-  left: 0.4rem;
+  left: 1.2rem;
   z-index: 5;
   pointer-events: none;
   color: var(--text-heading);