Lots of JS correctness fixes

 - Lots of files: Trailing comma on end of object
 - Lots of files: JSDoc fixes
 - Several files: Simplified return
 - `auto_close_form_component`: unnecessary escaping of `:` in regex
 - `lib/caret_position.js`: Redundant assignments
 - `lib/eyeline.js`: Unused variables
 - `app/jobs/scheduled/poll_mailbox`: Unused exception variable
 - `lib/page_tracker.js`: **Incorrect self/this usage**
 - `templates/components/category-drop`, `templates/composer/similar_topics`: Incorrect HTML
 - `lib/autocomplete.js`: Logic appears to be unused? Someone else figure it out, please.
 - `views/actions_history_view`: Use of uninitialized variable. Someone else figure this out, please.