Clean up all staticcheck errors (SA4006 + U1000): fix dead assignments in server_info.go and build_universal.go; remove unused proxy fields and functions; delete superseded icon_windows.go and shortcut_windows.go

server/internal/pool/proxy.go

@@ -66,7 +66,6 @@ type Proxy struct {
 	requestID      int
 	loginRequestID int
 	currentJob    *Job
-	jobSubscribed bool
 	stopCh         chan struct{}
 	wg             sync.WaitGroup
 	running        bool
@@ -844,30 +843,6 @@ func (j *Job) ToModelJob() *models.Job {
 	}
 }
 
-// Helper to convert target hex to difficulty
-func targetToDifficulty(targetHex string) int64 {
-	bytes, err := hex.DecodeString(targetHex)
-	if err != nil || len(bytes) == 0 {
-		return 0
-	}
-
-	// Reverse from little-endian
-	for i, j := 0, len(bytes)-1; i < j; i, j = i+1, j-1 {
-		bytes[i], bytes[j] = bytes[j], bytes[i]
-	}
-
-	target := new(big.Int).SetBytes(bytes)
-	if target.Sign() == 0 {
-		return 0
-	}
-
-	maxTarget := new(big.Int)
-	maxTarget.SetString("FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF", 16)
-	diff := new(big.Int).Div(maxTarget, target)
-
-	return diff.Int64()
-}
-
 // ParseBlob extracts fields from a Monero mining blob
 func ParseBlob(blobHex string) (map[string]interface{}, error) {
 	blob, err := hex.DecodeString(blobHex)