Add per-module code review tree under code-reviews/

Set up the code review process scaffolding adapted to mxaccessgw and
record a full per-module review of every src/MxGateway.* project at
commit 6c64030.

- code-reviews/_template/findings.md: per-module findings template
- code-reviews/regen-readme.py: generates README.md from findings.md
  files; --check fails if stale
- code-reviews/<Module>/findings.md: reviews for Contracts, Server,
  Worker, Tests, Worker.Tests, IntegrationTests (74 findings:
  1 Critical, 10 High, 23 Medium, 40 Low; all Open)
- code-reviews/README.md: generated cross-module index
- REVIEW-PROCESS.md: review process document

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

code-reviews/_template/findings.md

@@ -0,0 +1,53 @@
+# Code Review — <Module>
+
+<!-- Template for a per-module findings file. Copy to code-reviews/<Module>/findings.md.
+     See ../../REVIEW-PROCESS.md for the full process. The base README.md is generated
+     from these files by regen-readme.py — do not edit README.md by hand. -->
+
+| Field | Value |
+|---|---|
+| Module | `src/MxGateway.<Module>` |
+| Reviewer | <name> |
+| Review date | <YYYY-MM-DD> |
+| Commit reviewed | `<short-sha>` |
+| Status | Not started |
+| Open findings | 0 |
+
+## Checklist coverage
+
+A comprehensive review completes every category, recording "No issues found" where
+a category produced nothing rather than leaving it blank.
+
+| # | Category | Result |
+|---|---|---|
+| 1 | Correctness & logic bugs | _pending_ |
+| 2 | mxaccessgw conventions | _pending_ |
+| 3 | Concurrency & thread safety | _pending_ |
+| 4 | Error handling & resilience | _pending_ |
+| 5 | Security | _pending_ |
+| 6 | Performance & resource management | _pending_ |
+| 7 | Design-document adherence | _pending_ |
+| 8 | Code organization & conventions | _pending_ |
+| 9 | Testing coverage | _pending_ |
+| 10 | Documentation & comments | _pending_ |
+
+## Findings
+
+<!-- One ### entry per finding. IDs are <Module>-NNN, sequential within the module,
+     never reused. Findings are never deleted — close them by changing Status and
+     completing Resolution. -->
+
+### <Module>-001
+
+| Field | Value |
+|---|---|
+| Severity | Critical / High / Medium / Low |
+| Category | one of the 10 checklist categories |
+| Location | `path/to/File.cs:NN` |
+| Status | Open / In Progress / Resolved / Won't Fix / Deferred |
+
+**Description:** What is wrong and why it matters.
+
+**Recommendation:** Concrete suggested fix.
+
+**Resolution:** _(empty until closed; on close, record the fixing commit SHA, the date, and a one-line description of the fix)_