fix: Bitget WS keepalive — send text ping, not WebSocket PingMessage

Bitget v2 WS requires a text message "ping" every 30s, not a WebSocket
PingMessage control frame (opcode 0x9). Using the wrong ping type caused
a silent failure: connection stays up and subscription succeeds, but NO
ticker data is pushed — zero errors, zero reconnection logs.

Changes:
- connector.go: Add TextPing bool flag, send text 'ping' when set
- bitget.go: Set TextPing=true, handle text 'pong', add debug logging
- scanner.go: Expand to 179 overlapping Bitget+HL coins

main.go

@@ -76,13 +76,21 @@ func main() {
 	sigCh := make(chan os.Signal, 1)
 	signal.Notify(sigCh, os.Interrupt, syscall.SIGUSR1)
 
-	// Collect symbols
+		// Collect symbols — skip exchanges the coin isn't listed on
 	var bnSymbols, bgSymbols, hlSymbols, dydxSymbols []string
 	for _, c := range TrackedCoins {
-		bnSymbols = append(bnSymbols, c.BN)
-		bgSymbols = append(bgSymbols, c.BG)
-		hlSymbols = append(hlSymbols, c.HL)
-		dydxSymbols = append(dydxSymbols, c.HL)
+		if c.BN != "" {
+			bnSymbols = append(bnSymbols, c.BN)
+		}
+		if c.BG != "" {
+			bgSymbols = append(bgSymbols, c.BG)
+		}
+		if c.HL != "" {
+			hlSymbols = append(hlSymbols, c.HL)
+		}
+		if c.HL != "" {
+			dydxSymbols = append(dydxSymbols, c.HL)
+		}
 	}
 
 	// Start all exchange WS connections