Keep rotated log files for a set number of days

Personal-data catalog spec, default D1 (settled 2026-09-28): log files
were never deleted. inbuxa:LogSettings.keepForDays says how many days
rotated log files are kept; unset (null) keeps every file, as before,
and a new install sets 30 days.

It is a fork-owned setting, stored under T + l as audit retention is,
not a field on x:TracerLog: that object is also stored inside
x:Bootstrap with a field after it, so a new field would change
x:Bootstrap's stored format. Server-level, with the tracers'
permissions (sysTracerGet, sysTracerUpdate); changes are in the audit
log, before and after.

Log files are local, so every node deletes its own: hourly, and at once
when the setting changes on that node. Only regular files named
<prefix>.<something> in each enabled log tracer's directory, last
changed more than the limit ago, are removed; the file being written is
never that old, and nothing else in the directory is touched. Minimum
one day. The catalog classifies inbuxa:LogSettings and points the log
file's retention at it.

Tested: unit tests for the file rule (only this log's old files; the
current file, other files and directories stay) and a purge on disk;
the system suite, which reads, sets, refuses zero, restores null and
checks the audit records; fork checks.

crates/jmap/src/api/auth.rs

@@ -90,6 +90,8 @@ impl JmapAuthorization for AccessToken {
                 GetRequestMethod::DeletedAccount(_) => Permission::SysAccountGet,
                 // inbuxa: AI call limits, with the classifier's permissions
                 GetRequestMethod::AiLimits(_) => Permission::SysSpamLlmGet,
+                // inbuxa: log file retention, with the tracers' permissions
+                GetRequestMethod::LogSettings(_) => Permission::SysTracerGet,
                 // inbuxa: the audit log (AU-9)
                 GetRequestMethod::AuditEvent(_) | GetRequestMethod::AuditSettings(_) => {
                     Permission::SysAuditGet
@@ -201,6 +203,14 @@ impl JmapAuthorization for AccessToken {
                         Permission::SysSpamLlmUpdate,
                         Permission::SysSpamLlmUpdate,
                     ),
+                    // inbuxa: log file retention, with the tracers' permissions
+                    SetRequestMethod::LogSettings(s) => validate_set(
+                        s,
+                        self,
+                        Permission::SysTracerUpdate,
+                        Permission::SysTracerUpdate,
+                        Permission::SysTracerUpdate,
+                    ),
                     // inbuxa: the audit log (AU-7, AU-9, AU-11)
                     SetRequestMethod::AuditSettings(s) => validate_set(
                         s,
@@ -382,6 +392,7 @@ impl JmapAuthorization for AccessToken {
                 | MethodObject::MaskedEmail
                 | MethodObject::DeletedAccount
                 | MethodObject::AiLimits
+                | MethodObject::LogSettings
                 | MethodObject::Explanation
                 | MethodObject::AuditEvent
                 | MethodObject::AuditSettings