create colour scheme tructure

lua/paper-tonic-modern/groups/plugins.lua

@@ -0,0 +1,9 @@
+-- Paper Tonic Modern - Plugin Highlight Groups
+-- Highlights for various plugins (Telescope, Gitsigns, cmp, etc.)
+
+local colors = require('paper-tonic-modern.colors')
+
+return {
+  -- Plugin groups (to be implemented in Phase 11.8)
+  -- Telescope, Gitsigns, nvim-cmp, Oil.nvim, etc.
+}