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

Each database target now has its own archive file,
archive-WEBHOOKNAME-TARGETNAME-TARGETID.db, instead of one
archive-WEBHOOKID.db per webhook. delivery.ArchiveFileName builds the
name.

A change of webhook or target name renames its archive files under the
archive writer's lock, before the new name is saved, and back again if
the save fails. Webhook edits, target edits and target creation run one
at a time, so no two of them interleave. A rename never replaces a
file, and one that fails part way moves back what it moved. Deleting a
target evicts only that target's writer. Archive files are never
deleted, and nothing looks for files under the old name.

Model: opus-5-5

internal/server/routes_test.go

@@ -47,12 +47,18 @@ type noopNotifier struct{}
 
 func (n *noopNotifier) Notify([]delivery.Task) {}
 
-// noopEvictor satisfies handlers.New's delivery.WebhookEvictor
-// dependency. No test here checks what gets evicted, so it records
-// nothing.
-type noopEvictor struct{}
+// noopArchives satisfies handlers.New's delivery.Archives
+// dependency. No test here checks what gets evicted or renamed, so
+// it records nothing.
+type noopArchives struct{}
 
-func (e *noopEvictor) EvictWebhook(string) {}
+func (e *noopArchives) EvictWebhook(string) {}
+
+func (e *noopArchives) EvictTarget(string) {}
+
+func (e *noopArchives) Rename(_, _, _ string) error {
+	return nil
+}
 
 // testEnv is the real router from routes.go plus the collaborators
 // tests need to seed users and forge sessions.
@@ -117,7 +123,7 @@ func newTestEnvWithConfig(
 			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,