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

The event log now loads only the 50 newest events, limited in its query, and only the newest starts expanded; the rest start collapsed. Paging is removed rather than capped, since 50 events never need a second page: the Previous and Next links, the `page` query parameter and the page number Replay and Resubmit carried back are gone, and a `?page=` left in an old link shows the 50 newest. A webhook with more than 50 events reads "50 most recent of N events" beside the heading. Comments and a README line that called `page` the only query parameter the service reads now name `next` and `notice`.

Model: opus-5-5

internal/handlers/page_title_test.go

@@ -57,7 +57,11 @@ func TestEveryPageRendersItsOwnTitle(t *testing.T) {
 		},
 		{
 			"source_logs.html",
-			map[string]any{dataKeyWebhook: webhook, "TotalEvents": int64(0)},
+			map[string]any{
+				dataKeyWebhook: webhook,
+				dataKeyEvents:  []handlers.EventLogView{},
+				"TotalEvents":  int64(0),
+			},
 			"Full Event Log - orders - Webhooker",
 		},
 		{