Move nvim config into nvim/ subdirectory

Prepare repo structure for storing multiple dotfile configs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nvim/lua/plugins/colorscheme.lua

@@ -0,0 +1,8 @@
+return {
+  "p00f/alabaster.nvim",
+  priority = 1000,
+  config = function()
+    vim.o.background = "light"
+    vim.cmd.colorscheme("alabaster")
+  end,
+}