refactor: modularize nvim config into lua/config + lua/plugins

- Extract all options, keymaps, and autocommands into lua/config/
- Move every plugin spec into its own file under lua/plugins/
- Add custom inline orng colorscheme (dark + light) synced to macOS appearance
- Consolidate image.nvim into pdf-viewer.lua (fix duplicate spec)
- Fix image.nvim processor: magick -> magick_cli
- Remove conflicting nvim-autopairs (kept mini.pairs)
- Fix broken <C-f> keymap (was calling non-existent builtin cmd)
- Delete lua/kickstart/ and lua/custom/ folders
- Add colors/orng.vim + colors/orng-light.vim stubs for mid-session switching
- init.lua reduced from 1078 lines to 49 lines

lua/plugins/mini.lua

@@ -0,0 +1,32 @@
+-- lua/plugins/mini.lua
+-- mini.nvim collection: ai, pairs, animate, starter, surround, statusline
+
+return {
+  'echasnovski/mini.nvim',
+  config = function()
+    -- Better text objects: va) yi' ci{ etc.
+    require('mini.ai').setup { n_lines = 500 }
+
+    -- Auto-pairs for brackets, quotes, etc.
+    require('mini.pairs').setup()
+
+    -- Smooth scroll / cursor animations
+    require('mini.animate').setup()
+
+    -- Start screen
+    require('mini.starter').setup()
+
+    -- Surround: saiw) sd' sr)'
+    require('mini.surround').setup()
+
+    -- Statusline
+    local statusline = require 'mini.statusline'
+    statusline.setup { use_icons = vim.g.have_nerd_font }
+
+    -- Cursor position as LINE:COL
+    ---@diagnostic disable-next-line: duplicate-set-field
+    statusline.section_location = function()
+      return '%2l:%-2v'
+    end
+  end,
+}