Name each database target's archive for its webhook and target (closes #376)

Each database target now writes its own archive file, archive-WEBHOOKNAME-TARGETNAME-TARGETID.db, named by delivery.ArchiveFileName, in place of one archive per webhook keyed on its UUID. Renaming a webhook or a target renames its archive files (with any -wal and -shm) before the new name is saved, never over an existing file, and moves every one back if a rename or the save fails. The webhook edit, the target edit and target creation share one lock so no two interleave. Deleting a webhook or target leaves its files on disk. Nothing looks for the old archive-WEBHOOKID.db files. The README gives the naming and the recovery steps.

Model: opus-5-5

internal/resetpw/resetpw_test.go

@@ -132,9 +132,15 @@ type noopNotifier struct{}
 
 func (n *noopNotifier) Notify([]delivery.Task) {}
 
-type noopEvictor struct{}
+type noopArchives struct{}
 
-func (n *noopEvictor) EvictWebhook(string) {}
+func (n *noopArchives) EvictWebhook(string) {}
+
+func (n *noopArchives) EvictTarget(string) {}
+
+func (n *noopArchives) Rename(_, _, _ string) error {
+	return nil
+}
 
 // newServerApp starts the real login path against dir: the handlers,
 // the middleware that bounds password verification, the session store
@@ -167,7 +173,7 @@ func newServerApp(
 			healthcheck.New,
 			session.New,
 			func() delivery.Notifier { return &noopNotifier{} },
-			func() delivery.WebhookEvictor { return &noopEvictor{} },
+			func() delivery.Archives { return &noopArchives{} },
 			metrics.NewRegistry,
 			metrics.New,
 			middleware.New,