fix: correct Live 24/7 handling and label regressions

- stream.updateWithIssue: 'Live 24/7: Yes' meant the stream IS 24/7, but it
  was assigned straight to isNot247, inverting the label. A 'No' answer was
  also ignored because the guard skipped falsy values.
- dataSet.getBoolean: an unanswered dropdown is stored as '' by
  parseIssueBody, which getBoolean read as false. Treat it as undefined so
  'no answer' means 'leave unchanged' instead of 'Not 24/7'.
- update.addStream: has() is true for an unanswered field, so it produced
  isNot247 = true for issues that left the dropdown blank.
- generate: sortBy got five orders for four iteratees.
- 2_streams_edit.yml: restore the '~' reset option dropped from the quality
  dropdown when the Label field was removed.
- stream.getLabels: use const to satisfy prefer-const.

scripts/commands/playlist/generate.ts

@@ -52,7 +52,7 @@ async function main() {
       (stream: Stream) => (stream.isNot247 ? -1 : 0),
       (stream: Stream) => stream.getVerticalResolution()
     ],
-    ['asc', 'desc', 'desc', 'desc', 'asc']
+    ['asc', 'desc', 'desc', 'desc']
   )
 
   logger.info('filtering streams...')