Implement 'uninstall' command with clean removal

[y0s3ph]

Context

The `k8scope uninstall` command should cleanly remove all components and optionally their data (PVCs). It must handle partial installations gracefully.

Requirements

Uninstall flow

1. Detect installed components (via Helm releases with `k8scope` labels)
2. Show what will be removed
3. Ask for confirmation (unless `--confirm` flag)
4. Remove components in reverse dependency order:
   • OTel Collector (stop ingestion first)
   • Alertmanager
   • Grafana
   • Loki
   • Prometheus (last, as others depend on its CRDs)
5. Optionally remove PVCs (`--delete-data`)
6. Optionally remove namespace (`--delete-namespace`)
7. Optionally remove CRDs (`--delete-crds`)

Flags

• `--confirm` — Skip confirmation prompt
• `--delete-data` — Also delete PVCs (data loss warning)
• `--delete-namespace` — Delete the k8scope namespace
• `--delete-crds` — Remove Prometheus Operator CRDs (dangerous, affects other Prometheus installations)
• `--component prometheus` — Uninstall a single component

Safety

• Default behavior: remove releases only, keep PVCs and namespace
• `--delete-data` requires explicit confirmation even with `--confirm`
• Warn if CRD removal would affect other namespaces

Acceptance criteria

• Clean removal of all components
• PVCs preserved by default
• Works with partial installations (some components missing)
• Proper ordering prevents dangling resources
• `--delete-data` asks for explicit confirmation