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/config/options.lua

@@ -0,0 +1,49 @@
+-- lua/config/options.lua
+-- All vim options in one place
+
+local opt = vim.opt
+local o = vim.o
+
+-- Leader keys are set in init.lua before lazy loads
+
+-- UI
+o.number = true
+o.relativenumber = false
+o.cursorline = true
+o.signcolumn = 'yes'
+o.showmode = false
+o.scrolloff = 10
+o.splitright = true
+o.splitbelow = true
+o.inccommand = 'split'
+
+-- Characters
+o.list = true
+opt.listchars = { tab = '» ', trail = '·', nbsp = '␣' }
+
+-- Mouse
+o.mouse = 'a'
+
+-- Clipboard (deferred to avoid startup lag)
+vim.schedule(function()
+  o.clipboard = 'unnamedplus'
+end)
+
+-- Indentation
+o.expandtab = true
+o.smartindent = true
+o.tabstop = 2
+o.shiftwidth = 2
+o.breakindent = true
+
+-- Search
+o.ignorecase = true
+o.smartcase = true
+
+-- Files
+o.undofile = true
+o.confirm = true
+
+-- Performance
+o.updatetime = 250
+o.timeoutlen = 300