refactor(config): Update Emacs configuration across multiple modules

- Prefix gptel backend names with "gptel-" for consistency
- Add denote-org-backlinks-for-heading keybinding
- Refine recentf exclusions for org journal files
- Remove org-default-priority setting
- Add gptel and denote backlink buffer rules to ibuffer
- Enable markdown-ts-mode for Emacs 31+ with truncate lines
- Add electric-pair support for equals sign
- Update popper and window management regexes for new buffer names

lisp/init-kbd.el

@@ -194,7 +194,8 @@
   "C-," 'duplicate-and-move-to-next-line
   "C-c o l" 'denote-link
   "C-c o L" 'denote-org-link-to-heading
-  "C-c o b" 'denote-backlinks)
+  "C-c o b" 'denote-backlinks
+  "C-c o B" 'denote-org-backlinks-for-heading)
 
 ;; hs-hide-mode
 (general-def hs-minor-mode-map