Remove Aevo exchange (retired)

- Delete exchange/aevo.go (AevoWS, aevoTickerMsg, aevoTickerData, etc.)
- scanner.go: remove ExAevo constant, fee rates, scan pair entries, shortName mapping
- main.go: remove aevoSymbols collection loop and TrackedSymbol usage

main.go

@@ -71,16 +71,11 @@ func main() {
 
 	// Collect symbols
 	var bnSymbols, bgSymbols, hlSymbols, dydxSymbols []string
-	var aevoSymbols []exchange.TrackedSymbol
 	for _, c := range TrackedCoins {
 		bnSymbols = append(bnSymbols, c.BN)
 		bgSymbols = append(bgSymbols, c.BG)
 		hlSymbols = append(hlSymbols, c.HL)
 		dydxSymbols = append(dydxSymbols, c.HL)
-		aevoSymbols = append(aevoSymbols, exchange.TrackedSymbol{
-			Coin:         c.Name,
-			InstrumentID: c.Name + "-PERP",
-		})
 	}
 
 	// Start all exchange WS connections