audit: 2026-05-30 full-codebase audit — report, issues, docs, runbooks

Full-codebase-audit 2026-05-30 outputs:
- Audit report: 09 - Audits/Full Codebase Audit - 2026-05-30.md
- 81 issue files ISSUE-055..135 (decisions + 1 skipped no-brainer).
- Scanner docs from scratch (was zero): architecture, data model, API ref, payment
  flow, operations runbook + repo README.
- Doc-sync updates across API reference, data models, flows, design system.
- Secret Rotation Runbook (08 - Operations) for the exposed credentials.
- Reusable workflow guide (07 - Development) + .claude/workflows/full-codebase-audit.js.

Issues remain status:open intentionally — the code fixes are uncommitted-then-committed
working-tree changes per repo and aren't "resolved" until merged/deployed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Issues/ISSUE-123-backend-notification-unread-count-chatty-db-access.md

@@ -0,0 +1,38 @@
+---
+issue: 123
+title: "Backend: notification unread-count chatty DB access — 3 parallel countDocuments per event"
+severity: low
+domain: Notification
+labels: [performance, backend, database]
+status: open
+created: 2026-05-30
+source: Full Codebase Audit 2026-05-30
+---
+
+# Backend: notification unread-count chatty DB access — 3 parallel countDocuments per event
+
+**Severity:** low
+**Domain:** Notification
+**Labels:** performance, backend, database
+
+## Description
+
+`NotificationService.ts:145` runs 3 `countDocuments` calls per unread-count request. When notification events are frequent, this creates a high volume of DB count queries. Under heavy load, these compete with write operations.
+
+## Options
+
+1. Cache per-user unread count in Redis, increment/decrement on events.
+2. Coalesce the 3 parallel `countDocuments` into fewer aggregations.
+3. Leave as-is (covered by existing index) and only optimize if hot.
+
+## Recommendation
+
+Introduce a Redis-backed unread counter updated incrementally; until then, coalesce counts.
+
+## Affected Files
+
+- `backend/src/services/notification/NotificationService.ts:145`
+
+## References
+
+- [Full Codebase Audit 2026-05-30](../09%20-%20Audits/Full%20Codebase%20Audit%20-%202026-05-30.md) — DEC-44