Internet exposure checks and response rate limiting

Jarl works out which views are reachable from the internet (match-clients
ending in a catch-all, not private-looking addresses: an internal view of a
global IPv6 prefix is still yours; a server without views: open allow-query
and a non-private listen address), with a per-view override (schema 9), and
checks public ones: rate limiting, open resolver, minimal-any, cache
snooping, open NOTIFY and transfers, version and host name, management
interfaces. Fixes are staged like any change, including rate limiting from
ISC's example in log-only mode with the secondaries exempt, then enforcing.
named logs what rate limiting limits (or would, in log-only mode, where its
counters don't move) as query-errors; Jarl routes those lines to its log
and counts them (rrl breakdown, ratelimited top lists, Prometheus
jarl_ratelimit_logged_total), shown on the new Exposure page.

A change that newly opens a public view up must be confirmed (accept_risk,
--accept-risk, a checkbox on the Changes page; 409 confirm_risk
otherwise). Findings can be acknowledged with a reason and stay visible as
info. GET /exposure, POST /exposure/fix|ack|unack, jarl exposure,
docs/exposure.md.

Also fixes query statistics skipping TSIG-signed queries ("IP#port/key
NAME" in named's log).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/stats.md

@@ -103,6 +103,7 @@ lists, views, zones). named's own counters can't be filtered.
 | `zone:NAME` | response log | answers per local zone; `zone:-` for names in none of your zones |
 | `responses` | response log | lines read (a health check) |
 | `blocked`, `blocklist:NAME` | response log | queries [blocking](blocking.md) answered, and by which list (`blocklist:rules` for your own rules) |
+| `rrl:drop`, `rrl:slip`, `rrl:would-drop`, `rrl:would-slip` | response log | responses [rate limiting](exposure.md#response-rate-limiting) limited, or would have in log-only mode (named's own `ratelimit:*` counters don't move then) |
 
 **Server** (sampled every minute; stored as gauges, `g:KEY` the sum of
 the samples and `gn:KEY` their number, so a chart shows the average):
@@ -167,7 +168,8 @@ jarl stats top refused                     # who asks for what they may not have
 jarl stats timeline --since 6h             # sparkline; --table for every bucket
 jarl stats timeline --since 7d --key rcode:NXDOMAIN --key rcode:SERVFAIL
 jarl stats heatmap --since 28d
-jarl stats breakdown qtype | rcode | view | zone | answer | rtt | dnssec | cache | transport | ratelimit
+jarl stats breakdown qtype | rcode | view | zone | answer | rtt | dnssec | cache | transport | ratelimit | rrl
+jarl stats top ratelimited                 # client networks rate limiting limits (or would)
 jarl stats server                          # memory, CPU, cache, clients, host, disks now
 jarl stats timeline --since 7d --key g:named:rss --table   # named's memory over a week
 jarl stats summary --since 30d -o json     # export (also -o yaml)