feat(keymaps): diagnostic navigation respect count

- Multiply diagnostic jump count by vim.v.count1 so numeric prefixes are honored
- Preserve next/previous logic by keeping sign based on the `next` argument
- Leave severity and floating window behavior unchanged while fixing count handling

lua/lazyvim/config/keymaps.lua

@@ -122,7 +122,7 @@ end, { desc = "Format" })
 local diagnostic_goto = function(next, severity)
   return function()
     vim.diagnostic.jump({
-      count = next and 1 or -1,
+      count = (next and 1 or -1) * vim.v.count1,
       severity = severity and vim.diagnostic.severity[severity] or nil,
       float = true,
     })