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/request-timeout-scope.md

@@ -0,0 +1,50 @@
+---
+id: fix/request-timeout-scope
+name: Document request timeout scope and add Server header removal comment
+status: pending
+depends_on: []
+scope: single
+risk: trivial
+impact: isolated
+level: implementation
+review_findings: [S8]
+---
+
+## Description
+
+Review finding S8 notes that the request timeout applies to the entire HTTP exchange, not just the connection or first-byte response. For large file downloads or slow upstreams, this means a 60-second timeout kills the response even if the upstream is actively sending data.
+
+The review marks this as "acceptable for Phase 1" and the timeout name (`upstream_request_timeout_secs`) is documented as applying to the full request. However, the code should clearly document this behavior so it's not surprising.
+
+### Changes Required
+
+**`src/proxy/handler.rs`**:
+- Add a comment above the timeout wrapping in `proxy_handler`:
+  ```rust
+  // The timeout covers the entire HTTP round-trip including response body
+  // streaming. For large file downloads or slow upstreams, this means the
+  // timeout kills the response even if the upstream is actively sending data.
+  // A more precise timeout would apply only to connect + first-byte, then
+  // stream the body without a timeout. The `upstream_connect_timeout_secs`
+  // field in SiteConfig exists for a separate connect timeout (see W4).
+  // For Phase 1, this full-request timeout is acceptable.
+  ```
+
+## Acceptance Criteria
+
+- [ ] Comment documents the timeout scope
+- [ ] No code behavior change
+- [ ] `cargo clippy` passes with no warnings
+
+## References
+
+- docs/reviews/002-implementation-review.md — S8 finding
+- src/proxy/handler.rs — timeout wrapping
+
+## Notes
+
+> To be filled by implementation agent
+
+## Summary
+
+> To be filled on completion