Rip out compensating-controls framework (#359)

## Summary

Removes the compensating-controls (CC) framework. Prowler and Kingfisher continue to run weekly and produce reports; the Prowler mutelist YAML files stay in place but no longer carry \`CC: <id>\` prefixes — each entry now just keeps a free-form \`Description\` of why it's muted.

The CC review cadence proved to be more process overhead than this single-operator homelab needed.

## What changed

**Deleted**
- \`compensating-controls.yaml\` — the CC registry
- \`mise-tasks/review-compensating-controls\` — the staleness-review task
- \`docs/how-to/operations/review-compensating-controls.md\`
- \`docs/how-to/operations/record-review-evidence.md\` (was aspirational)
- \`docs/explanation/compliance-mute-categories.md\` (proposed-future CC/NA/RA work)
- 5 orphan \`+review-cc-*\` / \`+compliance-mute-categories\` changelog fragments

**Modified**
- 6 mutelist YAML files: stripped \`CC: <id>.\` prefix from every \`Description\` / \`statement\` field, kept the free-form text
- \`mise-tasks/review-compliance-reports\`: removed CC mentions from docstrings, panel text, and the node-verification table title. Node-verification logic itself is unchanged.
- \`docs/reference/operations/security.md\`: removed the "Compensating controls" section
- \`docs/how-to/operations/read-compliance-reports.md\`: rewrote step 3 of "Acting on findings" to point at the mutelist YAML directly
- \`docs/changelog.d/prowler-iac-mutelist.infra.md\`: rewrote to drop the "two new compensating controls" framing

## What did not change

- All Prowler manifests (cronjobs, RBAC, PVs, kustomization) — scans still run on the same schedule
- The Kingfisher deployment
- The trivy-shim in the Prowler container — that's about Trivy ignorefile plumbing, independent of the CC concept
- The mutelist entries themselves — each \`Resources\` list is unchanged; only the prose of \`Description\` was edited
- \`CHANGELOG.md\` — historical releases are left as-is

## Test plan

- [ ] Wait for human review before deploying — once merged, re-point ArgoCD: \`argocd app set prowler --revision main && argocd app sync prowler\` (no manifest changes besides the ConfigMap, so impact is limited to muted-finding descriptions in next week's report)
- [ ] Confirm next weekly Prowler K8s CIS run (Sunday 3am) still completes and produces a report on sifaka
- [ ] Confirm next weekly Prowler IaC run still honors \`trivyignore.yaml\` (the trivy shim is untouched but the ignorefile content was rewritten)
- [ ] \`mise run review-compliance-reports\` — verify node-verification block still runs and prints the renamed table title

Reviewed-on: #359

docs/reference/operations/security.md

@@ -46,13 +46,7 @@ Security posture and compliance scanning for BlumeOps infrastructure.
 
 All compliance scan reports are stored on `sifaka:/volume1/reports/`. See [[read-compliance-reports]] for access and interpretation.
 
-## Compensating controls
-
-Suppressed findings reference named compensating controls tracked in `compensating-controls.yaml` (repo root). Each control has a review date and verification steps. See [[review-compensating-controls]] for the review process.
-
-```bash
-mise run review-compensating-controls
-```
+Suppressed findings are kept in Prowler mutelist YAML under `argocd/manifests/prowler/mutelist/`. Each entry's `Description` field explains why the finding is muted; entries are reviewed ad-hoc rather than on a scheduled cadence.
 
 ## Known gaps