fix(client): close active NUI elements before opening new ones

[YgorLeal]

Summary

• Fixes NUI focus bugs when multiple ox_lib UI elements overlap (e.g., opening an inputDialog while a context menu is open)
• Root cause: keepInput in main.lua is a single variable that gets overwritten when a second UI opens, losing the original pre-NUI state
• Adds lib.closeAllNui(except) that cleanly closes all other open NUI elements before a new one opens

Changes

• main.lua: Added lib.closeAllNui(except) — closes context, menu, input, alert, and radial (with guards to avoid unnecessary resetNuiFocus calls)
• context.lua: lib.showContext() calls lib.closeAllNui('context') before opening
• input.lua: lib.inputDialog() calls lib.closeAllNui('input') before opening
• alert.lua: lib.alertDialog() calls lib.closeAllNui('alert') before opening
• menu.lua: lib.showMenu() calls lib.closeAllNui('menu') before opening

The except parameter ensures a UI type doesn't close itself (e.g., navigating between context sub-menus still works normally).

Test plan

• Open a context menu, then trigger an inputDialog via script — context should close, input should open cleanly
• Navigate context sub-menus — should work normally (except='context')
• Open an input dialog, then trigger an alert — input should close (resolves nil), alert should open
• Open a menu, then trigger a context menu — menu should close, context should open
• Close any UI normally (no other UI open) — should work exactly as before