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/handlers.go

@@ -30,10 +30,9 @@ import (
 const (
 	// maxBodyShift is the bit shift for 1 MB body limit.
 	maxBodyShift = 20
-	// recentEventLimit is the number of recent events to show.
+	// recentEventLimit is the number of most recent events that a
+	// webhook's page and its event log show.
 	recentEventLimit = 50
-	// paginationPerPage is the number of items per page.
-	paginationPerPage = 25
 
 	// tmplKeyError is the template data key for an error message.
 	tmplKeyError = "Error"