fix(cli): reject Count=0 and negative EstimatedSavings in CSV input #2116

From the review of #2114 (closes #1944). cmd/multi_service_csv.go ~185 still accepts an explicit Count of 0: it buys nothing but triggers a live purchase call ('About to buy 0 instances') that only AWS rejects (there's a provider zero guard for EC2 only). Change the check to n < 1 ('must be at least 1') and add a zero case to TestLoadRecommendationsFromCSV_StrictCount. The tool's own CSVs never emit 0 (the SP client sets Count: 1). Also reject a negative EstimatedSavings (~201), and stop printing the bad value twice in parse errors (%q plus a wrapped strconv.NumError, ~182/199).