Event log: only the newest event expanded, and only the 50 most recent (closes #349)

The event log now loads the 50 newest events in its query and opens
only the newest on load, as the recent events on a webhook's page
already do. With 50 at most there is never a second page, so paging is
gone: the page links, the `page` query parameter, the page number that
Replay and Resubmit carried back to the log, and `pageOrFirst` with its
test. The count beside the heading reads "50 most recent of N events"
when there are more. The comments and README lines that named `page` as
the query parameter the service reads now name `next` and `notice`.

Model: opus-5-5

internal/handlers/ui_copy_test.go

@@ -21,6 +21,7 @@ import (
 const (
 	dataKeyWebhook = "Webhook"
 	dataKeyError   = "Error"
+	dataKeyEvents  = "Events"
 )
 
 // testWebhookID is the identifier given to the webhook under test on
@@ -144,9 +145,10 @@ func TestEventLogPageIsCalledFullEventLog(t *testing.T) {
 	t.Cleanup(app.RequireStop)
 
 	// A pointer, as in the handlers: source_detail.html calls
-	// Webhook.RetentionLabel, a pointer method. Both pages only range
-	// over their lists, and a list left out renders as empty, so the
-	// lists are left out.
+	// Webhook.RetentionLabel, a pointer method. The webhook page only
+	// ranges over its lists, and a list left out renders as empty, so
+	// its lists are left out. The event log also counts its events, so
+	// it gets an empty list.
 	webhook := &database.Webhook{Name: "wh", RetentionDays: 14}
 	webhook.ID = testWebhookID
 
@@ -169,6 +171,7 @@ func TestEventLogPageIsCalledFullEventLog(t *testing.T) {
 
 	logBody := renderPage(t, h, sess, "source_logs.html", map[string]any{
 		dataKeyWebhook: webhook,
+		dataKeyEvents:  []handlers.EventLogView{},
 		"TotalEvents":  int64(0),
 	})
 
@@ -317,9 +320,9 @@ func TestEntrypointCopyButtonIsProgressiveEnhancement(t *testing.T) {
 		"Entrypoints": handlers.NewEntrypointViews(
 			[]database.Entrypoint{entrypoint},
 		),
-		"Targets": delivery.NewTargetViews(nil),
-		"Events":  []database.Event{},
-		"BaseURL": "https://hooks.example.com",
+		"Targets":     delivery.NewTargetViews(nil),
+		dataKeyEvents: []database.Event{},
+		"BaseURL":     "https://hooks.example.com",
 	})
 
 	assert.Contains(
@@ -384,9 +387,9 @@ func TestTargetFormMaxRetriesCopyMatchesBehaviour(t *testing.T) {
 			"Entrypoints": handlers.NewEntrypointViews(
 				[]database.Entrypoint{entrypoint},
 			),
-			"Targets": delivery.NewTargetViews(nil),
-			"Events":  []database.Event{},
-			"BaseURL": "https://hooks.example.com",
+			"Targets":     delivery.NewTargetViews(nil),
+			dataKeyEvents: []database.Event{},
+			"BaseURL":     "https://hooks.example.com",
 		},
 	)