inbound-antispam-panel: filter lists, written as rspamd maps

Step 5/12 of docs/plans/inbound-antispam-panel.md.

Store: AddSpamListEntry, ListSpamListEntries, DeleteSpamListEntry.
internal/inbound/lists.go validates and normalises an entry - sender
address, sender domain, client address or network (canonical text, an
IPv4-mapped address as IPv4, /0 refused) - and writes the lists as six
map files under /data/antispam (ANTISPAM_DIR), each atomically, 0644 in
a 0755 directory: the filter is another user in another container. All
six are written on every change and on every start with the relay on,
empty ones included. An entry whose maps could not be written is taken
back out of the table. The writer refuses a stored value with
whitespace, a newline or # in it.

The plan's allow.map / deny.map became one file per list and entry
type: to rspamd an IP map and a sender map are different map types.

deploy/antispam/rspamd/multimap.conf holds the rules; the fragment
mounts it and ./data/antispam into the sidecar. Deny is a prefilter
reject, allow a symbol weighing -100. Tried in a throwaway rspamd 3.11
container on the test server:
  - with allow as a prefilter accept, an address on both lists was
    accepted and an IP on both was refused - the rule that ran first
    decided; with the weight, deny won in all five mixed cases;
  - IPv4, IPv6, address (any case), domain (not its subdomains) match;
  - a rewritten file is reread in about ten seconds, no restart;
  - files that appear after rspamd started are loaded the same way.

No page edits the lists yet (step 6).

Checked on the test server, uncommitted tree: go vet ./... ok,
go test ./... ok (22 packages), make e2e ok - with the relay on
/data/antispam is 755 and holds the six maps, 644, empty.

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

test/e2e/port25_features_test.go

@@ -268,6 +268,23 @@ func testInboundRelay(t *testing.T, sc *scenario) {
 	// The inbound journal milter saw it go through. No page shows the journal
 	// yet, so the row is read where it is kept. No filter is attached on the
 	// stand: the row is an accept by nobody.
+	// The filter lists exist as files from the first start with the relay on,
+	// readable by a filter that is another user in another container. Nothing
+	// is on them: no page edits them yet.
+	maps, err := h.execIn("selfpost", "sh", "-c", `cd /data/antispam && stat -c "%a %n" . *.map && { grep -vc "^#" *.map; true; }`)
+	if err != nil {
+		t.Fatalf("list /data/antispam: %v\n%s", err, maps)
+	}
+	for _, want := range []string{"755 .",
+		"644 allow_domain.map", "644 allow_from.map", "644 allow_ip.map",
+		"644 deny_domain.map", "644 deny_from.map", "644 deny_ip.map",
+		"allow_ip.map:0", "deny_from.map:0",
+	} {
+		if !strings.Contains(maps, want) {
+			t.Fatalf("/data/antispam: no %q in\n%s", want, maps)
+		}
+	}
+
 	// journalHas waits for a row and returns the journal as it then stands.
 	journalHas := func(want string) string {
 		t.Helper()