Restructure modules/shared and update all imports

- Delete 2024-12-rework/ folder
- Rename modules/hosts/common to modules/shared, then split into:
  - modules/shared/home/general
  - modules/shared/home/linux
  - modules/shared/nixos
- Update all import paths throughout the codebase
- Update lib/*.nix to use new paths
- Fix hardcoded /Users/${username} to use config.home.homeDirectory
- Update README and examples/flake-structure.nix

modules/shared/files/nvim/lua/disabled/nvim-tree.lua

@@ -0,0 +1,11 @@
+return{
+  "nvim-tree/nvim-tree.lua",
+  config = function ()
+    vim.g.loaded_netrw = 1
+    vim.g.loaded_netrwPlugin = 1
+
+    require('nvim-tree').setup()
+
+    vim.keymap.set('n', '<c-n>', ':NvimTreeFindFileToggle<CR>')
+  end
+}