Journaling: capture at the queue, the built-in journal, retention

Phase 2 of the journaling spec.

- A copy of each message is taken in MessageWrapper::queue, after DLP and
  transport rules, for every enabled journal that takes it (direction and
  scope: everyone, or accounts, groups, domains, tenants). If the copy
  can't be taken the message isn't queued (temporary failure).
- The journal report: the envelope one field a line (sender, To, Cc, Bcc
  from the envelope, list members from their ORCPT, direction, held for
  review), then the queued message byte for byte as message/rfc822.
- The built-in journal under J in the inbuxa subspace: one chain per node
  whose links name each entry by SHA-256, so entries can expire out of
  chain order; purge leaves a marker, and verify catches an entry changed
  or removed early and a report that doesn't match.
- Retention per journal (30 to 3650 days); an entry keeps what it was
  written with. The daily maintenance purges what's due, keeping entries
  whose people a legal hold covers (deleted accounts a hold keeps too),
  and records the counts in the audit log.
- inbuxa:Journal get/set, audited by the request layer. Permissions
  680-683: administrators see and change journals; the Compliance Officer
  sees, searches and exports. Whoever changes journals may grant search and
  export without holding them, so officers can still be appointed.
- Catalog entries (inbuxa:Journal, source "journal"); spec as-built notes.

tests/src/system/journal.rs: validation, internal mail with a Bcc,
outgoing into two journals, incoming over LMTP, the report and its
original, tamper and early removal caught, hold-aware purge, retention
changes leave entries alone, disabled and removed journals take nothing.

crates/common/src/manager/granted_permissions.rs

@@ -52,6 +52,8 @@ const ADMIN_GRANTS: &[Permission] = &[
     Permission::SysDlpPolicyUpdate,
     Permission::SysDlpReviewGet,
     Permission::SysDlpReviewUpdate,
+    Permission::SysJournalGet,
+    Permission::SysJournalUpdate,
 ];
 
 /// Granted to the server-level Compliance Officer role once it exists:
@@ -61,6 +63,10 @@ const OFFICER_GRANTS: &[Permission] = &[
     Permission::SysDlpPolicyGet,
     Permission::SysDlpReviewGet,
     Permission::SysDlpReviewUpdate,
+    // journaling spec, JR-18: see journals, search and export them
+    Permission::SysJournalGet,
+    Permission::SysJournalSearch,
+    Permission::SysJournalExport,
 ];
 
 /// Granted to the default tenant administrator roles: reading and exporting