[fix](trx-frontend-http): stabilize signal strength field width and BW overlay positioning

Increase sig-strength-display min-width to 7.5rem so the field no longer
resizes when the value switches between two-digit and three-digit numbers.

Reposition the fast BW overlay immediately when bandwidth changes arrive
via SSE, and force-display on bookmark apply so freq+bw render atomically
instead of the BW bars wiggling from a stale intermediate state.

https://claude.ai/code/session_01R2XBFEBL8CrsTx5inu25MA
Signed-off-by: Claude <noreply@anthropic.com>

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

@@ -629,7 +629,7 @@ button:disabled { opacity: 0.6; cursor: not-allowed; }
   flex-shrink: 0;
 }
 .sig-strength-display {
-  min-width: 5.2rem;
+  min-width: 7.5rem;
   height: 3.35rem;
   padding: 0 0.7rem;
   border: 1px solid var(--border-light);