feat: setup logs retention by max file size

features/activity-log-backend.feature

@@ -30,7 +30,7 @@ Feature: The back-office keeps an append-only activity log that owners can read
         | change.kind | text, body                                      |
 
     Scenario: The repository exposes no way to edit or delete one event
-      Then the audit Repository interface has exactly the methods Append, List, Summary and DeleteOlderThan
+      Then the audit Repository interface has exactly the methods Append, List, Summary, DeleteOlderThan, DeleteOldest and SizeBytes
       And the persistence implementation exposes no other exported method than those and its constructor
       And the HTTP surface has no POST, PUT, PATCH or DELETE under /v1/activity
 
@@ -464,7 +464,7 @@ Feature: The back-office keeps an append-only activity log that owners can read
         | 2026-10-06T03:00:00 | 2026-10-06T04:00:00 | false |
         | 2026-10-06T03:00:00 | 2026-10-07T03:00:00 | true  |
 
-    Scenario: Forever never runs
+    Scenario: Forever with no size limit never runs
       Given the retention is 0
       When Tick runs at 2026-10-06T03:00:00
       Then ran is false and DeleteOlderThan is not called
@@ -559,3 +559,10 @@ Feature: The back-office keeps an append-only activity log that owners can read
       When the owner sends GET /v1/activity
       Then the three events are listed newest first with their documented items
       And GET /v1/activity?security=true lists only the failed login
+
+    Scenario: The size limit extension amends the retention rules
+      Given features/activity_home_card_and_retention.feature, rule "Retention size limit"
+      Then the settings default also has activity_retention_max_gb 0 and activity_log_size_bytes 0
+      And PATCH /v1/settings also accepts activity_retention_max_gb validated against audit.SizeOptions()
+      And the last 24 hours are never removed by DeleteOldest either
+      And a retention change is recorded with the max_gb_from and max_gb_to params when the size changes