Use one name for each thing the UI shows (closes #399)

The UI gave one thing several names. The `database` type is now Archive in the type list, on its badge and on the edit page, and its settings read "Archive expiry" and "Archive rotation" everywhere. The retry field is "Delivery attempts", with help text, errors and the target list saying it counts every attempt; a stored 0 shows as one attempt. The target list uses one capitalisation. The navbar says "Sign out", the sign-in page "Sign in", and the resubmit notice "webhook" instead of "source". The README follows. Stored values, their meaning, routes and form field names are unchanged.

Model: opus-5-5

internal/handlers/target_retries.go

@@ -25,14 +25,14 @@ var (
 	// errRetriesInvalid signals a max_retries form value that is not
 	// a non-negative whole number.
 	errRetriesInvalid = errors.New(
-		"retries must be a whole number of attempts",
+		"must be a whole number",
 	)
 
 	// errRetriesTooLarge signals a max_retries form value that is a
 	// whole number but above maxTargetRetries. It is distinguished
 	// from errRetriesInvalid so the message can name the ceiling
 	// instead of implying the input was not a number.
-	errRetriesTooLarge = errors.New("retries out of range")
+	errRetriesTooLarge = errors.New("out of range")
 )
 
 // parseMaxRetries interprets a max_retries form value.
@@ -82,7 +82,7 @@ func retriesErrorMessage(err error) string {
 	if errors.Is(err, errRetriesTooLarge) {
 		return errRetriesTooLarge.Error() +
 			": at most " + strconv.Itoa(maxTargetRetries) +
-			" retries"
+			" attempts"
 	}
 
 	return errRetriesInvalid.Error() +