feat(nvim): phase 2 — replace nvim-notify and dressing with snacks

Enable snacks.input and snacks.notifier modules; remove the
now-redundant nvim-notify and archived dressing.nvim specs.
Notifier preserves the prior icons and 3000 ms timeout.

lua/absolute/plugins/snacks.lua

@@ -6,7 +6,20 @@ return {
 	opts = {
 		bigfile = { enabled = true },
 		quickfile = { enabled = true },
-		-- input, notifier added in Phase 2
+		input = { enabled = true },
+		notifier = {
+			enabled = true,
+			timeout = 3000,
+			style = "compact",
+			top_down = true,
+			icons = {
+				debug = "",
+				error = "",
+				info = "",
+				trace = "✎",
+				warn = "",
+			},
+		},
 		-- picker added in Phase 3
 	},
 }