[Audit] Runtime stability and security remediation tracker

## Summary

This issue tracks remediation of the agreed runtime and security audit for the custom `academyAfrica` theme, `academy-africa` plugin, and `academy-error-logger.php` mu-plugin on the `develop` branch.

Security-sensitive P0 findings are tracked separately in a private draft security advisory. This public tracker intentionally excludes exploit details.

## Workstreams

### P0 — Catastrophic latent reliability

- [x] #45 — Remove dependency on `short_open_tag`

### P1 — Authentication and critical user flows

- [x] #56 — Consolidate account verification and activation state
- [x] #54 — Repair registration, login, and password-reset flows
- [x] #46 — Restore LearnDash progression and certificate resilience
- [x] #57 — Harden event rendering and query performance

### P2 — Correctness, performance, and frontend runtime

- [ ] #49 — Correct course metadata, filtering, and sorting
- [ ] #50 — Harden shared template data and post-type configuration
- [ ] #47 — Make custom cache invalidation reliable
- [ ] #52 — Reduce diagnostic overhead and preserve admin Heartbeat
- [ ] #51 — Repair asset dependencies and conditional loading
- [ ] #55 — Harden frontend JavaScript, markup, and output handling

### P3 and quality controls

- [x] #53 — Remove duplicate and dead theme/plugin code
- [ ] #48 — Add runtime and security regression gates

## Recommended sequence

1. Complete and verify the private security remediation.
2. Remove the short-tag dependency.
3. Repair authentication, account, LearnDash, and event flows.
4. Address data correctness, caching, runtime overhead, assets, and frontend resilience.
5. Complete cleanup and enforce regression gates in CI.

## Exit criteria

- All P0–P2 workstreams are closed with verification evidence.
- Private security findings are remediated and validated.
- Critical account, LearnDash, event, and course flows pass regression testing.
- CI prevents the identified runtime and security failure classes from recurring.
- Staging verification is recorded before production rollout.