Config: extract keybinding functions and clean up key configs

- Add init-kbd-func.el for keybinding helper functions
- Move global-display-line-numbers-mode from early-init.el to init.el
- Slim down init-kbd.el: remove hydra-multiple-cursors, migrate defs
- Reorganize dirvish config
- Remove scattered global-set-key bindings from init-org, init-ui, etc.
- Guard server-start with server-running-p check
- Set ibuffer-default-sorting-mode to filename
- Tweak gptel config

init.el

@@ -13,6 +13,8 @@
 (when (file-exists-p custom-file)
   (load-file custom-file))
 
+(global-display-line-numbers-mode t)
+
 (require 'init-const)
 (require 'init-startup)
 (require 'init-elpa)
@@ -27,6 +29,7 @@
 (require 'init-gptel)
 (require 'init-workspace)
 (require 'init-ui)
+(require 'init-kbd-func)
 (require 'init-kbd)
 (require 'init-segmentation)