send log: rows belong to a domain by id (audit L12, 0008)

A domain user's log, the message page, a domain's statistics, the level-2
count and the notifier's refusal count picked send-log rows by domain name,
so a domain deleted and re-added under its old name showed its earlier mail
to the next assignee and went on counting it.

Migration 0008 (not run on the live database yet, so extended here):
send_log.domain_id and inbound_spam_log.inbound_domain_id, REFERENCES ...
ON DELETE SET NULL, filled once by name from the registry as it is at
migration time, each with an (id, created_at) index.

- Writes: InsertQueued / InsertRejected set domain_id to the domain of the
  row's login (loginDomainID) - the journal milter and the sender check's
  refusal rows both go through them; the inbound journal sets
  inbound_domain_id from the inbound domain's name at insert.
- Reads: SendLogFilter.DomainIDs (was Domains, by name) and
  InboundSpamFilter.DomainIDs are the scope; the global role still reads
  everything. The message page checks row.DomainID against the user's
  domains. DomainSendStats and CountMessages keep their name argument and
  select domain_id = (SELECT id FROM domains WHERE name = ?). The notifier
  joins send_log.domain_id to the domain and its application.
- DMARC reports stay by name on purpose (a report is about the DNS name).

Tests: store - scope by ids; a re-added domain's log, level-2 count and
statistics hold its own row only, the global log both; inbound scope by
ids. Handlers - the new assignee gets 404 for the old row's page and does
not see it in the log, the global role sees both. Tests that wrote rows for
a login that is no application now register it (a row is a domain's through
its application). Schema at 0008 with the two columns and indexes.

schema-migrations row 8, CHANGELOG [Unreleased], audit plan line ticked,
roadmap 19/62.
Evidence: go vet ./... clean; go test ./... ok locally but for the two
Windows-only tests; the server run follows before the push.

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

internal/store/migrations/0008_tenant_boundary.sql

@@ -9,3 +9,20 @@
 -- (case-sensitive) stays: SQLite cannot change a column's collation without
 -- rebuilding the table, and this index is the stricter rule.
 CREATE UNIQUE INDEX idx_applications_login_nocase ON applications (login COLLATE NOCASE);
+
+-- A send-log row belongs to a domain by its id, not its name (audit L12; the
+-- owner, 2026-10-12). A domain deleted and added again under its old name
+-- used to show the earlier rows to whoever it was assigned to next. The id is
+-- the domain of the login the row was written for; a row of a domain deleted
+-- since - and every row older than this migration whose domain is gone - is
+-- NULL and nobody's but the global role's. The name stays for display and for
+-- the global view. Filled once from the registry as it is now.
+ALTER TABLE send_log ADD COLUMN domain_id INTEGER REFERENCES domains(id) ON DELETE SET NULL;
+UPDATE send_log SET domain_id = (SELECT d.id FROM domains d WHERE d.name = send_log.domain);
+CREATE INDEX idx_send_log_domain_id_created_at ON send_log (domain_id, created_at);
+
+-- The inbound journal follows the same rule, so the two logs do not follow two
+-- (security.md's accepted risk of the inbound log, struck).
+ALTER TABLE inbound_spam_log ADD COLUMN inbound_domain_id INTEGER REFERENCES inbound_domains(id) ON DELETE SET NULL;
+UPDATE inbound_spam_log SET inbound_domain_id = (SELECT d.id FROM inbound_domains d WHERE d.name = inbound_spam_log.inbound_domain);
+CREATE INDEX idx_inbound_spam_log_domain_id_created_at ON inbound_spam_log (inbound_domain_id, created_at);