FinOps grade cost analysis v0.6.0

• Add --breakdown deployment flag: per-Deployment/StatefulSet/DaemonSet cost drill-down in CLI
• Add HTML cost dashboard (--format html): KPI cards, share bars, waste, score bars, optimization scenario cards, assumptions footnotes
• Remove spot instance scenarios; replace with right-sizing, idle workload, and namespace consolidation scenarios
• Exclude system namespaces (kube-system, cert-manager, istio-system, monitoring, flux-system, etc.) from optimization recommendations and deployment breakdown
• Make --monthly-cost optional: resource-share mode when no billing data
• Add unallocated row reconciling namespace allocations vs cluster total
• Fix idle pod detection: allow up to 5 restarts (was 0, broke all
  production pods); require 7+ day age threshold
• Fix confidence scoring: 3-signal model (share size + pod count +
  waste); replaces share-size-only logic that returned Medium for ~95% of namespaces
• Add wasteColor, mul template FuncMap helpers in costs_html.go
• Bump version to 0.6.0; update README with all changes

What's Changed

• Feature/enhance report by @opscart in #5

Full Changelog: v0.5.3...v0.6.0