feat(nvim): phase 3 — replace nvim-cmp with blink.cmp and telescope with snacks.picker

Swap the completion engine to blink.cmp v1.x, dropping nvim-cmp,
its eight cmp-* sources, lspkind, and LuaSnip. Swap the picker
to snacks.picker, removing telescope.nvim and six telescope
extensions. LSP capabilities now sourced from blink.cmp; LSP
navigation keymaps and the colorscheme/keymaps/todo pickers move
to Snacks.picker. friendly-snippets is preserved as blink's
snippet source.

lua/absolute/plugins/blink-cmp.lua

@@ -0,0 +1,9 @@
+return {
+	"saghen/blink.cmp",
+	version = "1.*",
+	event = "InsertEnter",
+	dependencies = { "rafamadriz/friendly-snippets" },
+	config = function()
+		require("absolute.after.blink-cmp")
+	end,
+}