refactor: reuse the existing service and rendering helpers

services.IsNotFound replaces the hand-rolled 404 checks, convertPage
the copied page conversions and lastPathNumber the comment's own
number parser. The List wrappers around ListPage of releases,
branches, wiki pages, secrets and variables go, pull request filters
resolve milestones through Milestones.FindOne like issues, and
localFlagsChanged, boolOrder, Cell.Render, stateBadge and dueText
replace their copies.

Signed-off-by: bircni <bircni@icloud.com>

internal/services/errors.go

@@ -194,6 +194,12 @@ func Classify(err error, kind, key, scope string) error {
 	return err
 }
 
+// IsNotFound reports whether err is a 404 response.
+func IsNotFound(err error) bool {
+	failure, ok := errors.AsType[*transport.APIError](err)
+	return ok && failure.Status == http.StatusNotFound
+}
+
 // refusal returns the conflict reason of a refused request, or "".
 func refusal(apiErr *transport.APIError) string {
 	if apiErr.Status == http.StatusLocked {