Decompose implementation review fixes into 14 atomic tasks with post-fix review

Break down findings from review #002 into dependency-ordered fix tasks:

Critical/High:
- fix/acme-contact-and-challenge (C1+C2): Add acme_contact field, wire to
  ACME, remove unused challenge_config, add validation rule 19
- fix/remove-health-and-hardcode-https (W5+W14+ADR-022): Remove /health
  from main listener, hardcode X-Forwarded-Proto to https
- fix/config-reload-static-drift (C4): Use ArcSwap<StaticConfig> so reload
  diffs against last config, not startup config
- fix/access-logging (W13): Wire up log_request! macro for every proxied
  request with client_ip, host, method, path, status, upstream, duration_ms

Medium:
- fix/graceful-shutdown (W1+W7): Join HTTPS tasks with timeout instead of
  abort, add shutdown signal to admin socket and eviction task
- fix/connect-timeout (W4): Wire upstream_connect_timeout_secs to enforce
  separate connect timeout

Low/Independent:
- fix/token-bucket-nanosecond (W6): Use as_nanos() instead of as_millis()
- fix/normalize-host-ipv6 (S3): Handle IPv6 bracket notation in normalize_host
- fix/http-port-validation (S1): Validate http_port in range 0 or 1-65535
- fix/integration-test-toml (S10): Fix double-nested listeners.listeners.sites
- fix/logging-test-global-subscriber (W9): Use try_init() to avoid test conflicts
- fix/fragile-error-detection (W3): Add typed error matching or documented string match
- fix/add-code-comments (C3,W8,W10,W11,S9): Document correct-but-non-obvious behaviors
- fix/request-timeout-scope (S8): Document full-request timeout scope
- fix/clean-dead-code (S4+S2): Remove dead_code annotations, add #[non_exhaustive]

Review gate:
- review/post-fix-review: Verify all fixes against architecture spec

tasks/fix/integration-test-toml.md

@@ -0,0 +1,44 @@
+---
+id: fix/integration-test-toml
+name: Fix double-nested listeners.listeners.sites in integration test TOML
+status: pending
+depends_on: []
+scope: single
+risk: trivial
+impact: isolated
+level: implementation
+review_findings: [S10]
+---
+
+## Description
+
+The `write_valid_config` helper in `tests/integration_test.rs:514` contains `[[listeners.listeners.sites]]` which is a double-nested TOML path that doesn't match the config schema. The correct key is `[[listeners.sites]]`.
+
+The test passes because it's used as an invalid config fixture (the binary validates and exits with error), but the function name `write_valid_config` suggests it was intended to produce valid config.
+
+### Changes Required
+
+**`tests/integration_test.rs`**:
+- Fix the TOML key from `[[listeners.listeners.sites]]` to `[[listeners.sites]]`
+- If the function was intended to produce valid config, verify the test still passes with the corrected TOML
+- If the function is deliberately producing invalid config for a validation test, rename it to `write_invalid_config` or add a comment explaining the intentional invalidity
+
+## Acceptance Criteria
+
+- [ ] TOML nesting is corrected to `[[listeners.sites]]`
+- [ ] Test function name matches its purpose (valid or invalid config)
+- [ ] All integration tests pass
+- [ ] `cargo test` passes
+
+## References
+
+- docs/reviews/002-implementation-review.md — S10 finding
+- tests/integration_test.rs — `write_valid_config` helper
+
+## Notes
+
+> To be filled by implementation agent
+
+## Summary
+
+> To be filled on completion