Connections, "every packet" rules, and a packet tracer

- Connections: the kernel's tracked connections, read and closed over
  ctnetlink (internal/conntrack, raw netlink like the drop log), with
  their NAT and TCP state; closing one makes the rules check its next
  packet again (GET /connections, POST /connections/close; hc
  connections; Traffic → Connections).
- Rules can check every packet (every_packet, --every-packet): before
  established connections are accepted, so a drop or reject also stops
  connections already open. They can't accept.
- A packet tracer (internal/trace): a table of its own, inet
  housecarl-trace, marks the packets a filter picks, `nft monitor trace`
  reports every rule and policy they meet in every table, and the tracer
  names what accepted or dropped them, Housecarl's rules by name (POST,
  GET, DELETE /trace; hc trace; Traffic → Trace). One trace at a time,
  at most 200 packets and 20 a second; the table goes when it ends.

e2e: 157 checks, among them an upload a normal block doesn't stop and an
every-packet one does, and a trace naming the blocking rule.

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

docs/cli.md

@@ -137,6 +137,8 @@ by name.
 | `counters` | the hits of every rule, NAT rule, built-in and policy, by mark (`r12`, `f3`, `b-established`, `p-input`) |
 | `quotas` | what each rule's quota used (each address's, for per-address quotas), and when it resets |
 | `log [-f] [--search TEXT] [--limit N]` | the packets logged by rules and policies ([operations.md](operations.md#the-log)) |
+| `connections [--search TEXT] [--limit N]`, `connections close --search TEXT [-y]` | tracked connections; closing makes the rules check them again ([operations.md](operations.md#connections)) |
+| `trace [--address A] [--port N] [--protocol P] [--seconds S]` | follow packets through every table's rules ([operations.md](operations.md#tracing)) |
 
 ### zone, set, service
 
@@ -182,7 +184,7 @@ The match flags (`rule add`, `snat add`, `redirect add`):
 And for rules: `--state`, `--status`, `--days`, `--hours`, `--limit
 10/minute|1mbytes/second[,burst=N][,over][,per-source|,per-destination]`,
 `--quota 50gbytes[,over][,per-source|,per-destination][,daily|,weekly|,monthly=DAY]`,
-`--group-v4 N`, `--group-v6 N`, `--conn-limit N`, `-a
+`--group-v4 N`, `--group-v6 N`, `--conn-limit N`, `--every-packet`, `-a
 accept|drop|reject|log`, `--reject-with tcp-reset`, `--log`,
 `--log-prefix`, `--raw RULE`, `--comment`, `--disabled`
 ([rules.md](rules.md#rules)).