fix: probe 400000 baud first and relax FC stale threshold

CP210x chips can't hit 921600 exactly so try 400000/420000 first.
Raise FC_STALE_S from 2s to 5s so the dashboard doesn't flicker
STALE when FC telemetry arrives slowly.

tools/telemetry.c

@@ -17,7 +17,7 @@
 #endif
 
 /* Probe bauds: CP210x chips on ELRS can't hit 921600 exactly. */
-static int const s_probe_bauds[] = {921600, 400000, 420000};
+static int const s_probe_bauds[] = {400000, 420000, 921600};
 static int const s_probe_bauds_count =
     (int)(sizeof(s_probe_bauds) / sizeof(s_probe_bauds[0]));
 
@@ -79,7 +79,7 @@ static void ansi_cursor_up(int n) {
 /* --------------------------------------------------------------------------- */
 
 #define LINK_STALE_S 3.0f
-#define FC_STALE_S 2.0f
+#define FC_STALE_S 5.0f
 
 typedef enum {
     STATUS_LIVE,