Rewrite price lookup from WebSocket to REST API

Replace unreliable WebSocket connections with on-demand REST API calls
for spot and futures prices. Add cached trading pair list (refreshed
hourly) for symbol validation, and /refresh command for manual updates.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

internal/services/tele/command.go

@@ -16,6 +16,10 @@ var commandList = []telebot.Command{
 		Text:        "fee",
 		Description: "(f) - show top funding fee",
 	},
+	{
+		Text:        "refresh",
+		Description: "Refresh trading pair cache",
+	},
 }
 
 func setupCommands(b *telebot.Bot) error {
@@ -36,6 +40,7 @@ func setupCommands(b *telebot.Bot) error {
 	//info
 	b.Handle("/p", commands.OnGetTopPrices)
 	b.Handle("/fee", commands.OnGetTopFundingFee)
+	b.Handle("/refresh", commands.OnRefreshPairCache)
 
 	//any text
 	b.Handle(telebot.OnText, commands.OnChatHandler)