ui_app_setup: drop HAL_PLATFORM_SDL guard so emulator builds

[eggfly]

Summary

Make UISetupPage compile on the emulator (macOS / SDL Linux / Web) so the SETTING page is actually reachable from APPLaunch.

Problem

ui_app_launch.cpp:144:67: error: 'UISetupPage' was not declared in this scope
                              img_path("setting_100.png"), page_v<UISetupPage>);
                                                                  ^~~~~~~~~~~

ui_app_setup.hpp is currently wrapped in #if !defined(HAL_PLATFORM_SDL), which excludes it from emu builds — but ui_app_launch.cpp registers page_v<UISetupPage> unconditionally, so the build is structurally broken under HAL_PLATFORM_SDL.

This breaks the M5CardputerZero-Emulator CI on every platform.

Fix

Drop the SDL guard. The class is already HAL-clean for the parts the emu actually exercises:

• ✅ Uses HAL: hal_wifi_*, hal_battery_*, hal_volume_*, hal_bt_*, hal_backlight_* — all have stubs in hal/sdl/.
• ✅ i2c ioctl / <linux/i2c.h> includes — already inside #ifdef __linux__.
• ⚠️ Residual unguarded raw syscalls (popen, system, /sys/class/power_supply walk):
  • These are POSIX, compile fine on macOS/Linux hosts.
  • They're only triggered when the user navigates to specific sub-pages (Account / Ethernet / Update / Set RTC) and confirms an action — flows the emulator user can't reach without explicit input. So compiling them in isn't a runtime hazard either.
  • Follow-up: route them through hal_account_info() / hal_eth_status() / hal_system_update_*(). Out of scope for this PR.

Test

Local macOS arm64 (with M5CardputerZero-Emulator submodule pointing at this branch):

$ make -C build -j10
[100%] Built target cardputer-emu
$ file build/cardputer-emu
build/cardputer-emu: Mach-O 64-bit executable arm64
$ ./build/cardputer-emu  # opens, SETTING page now reachable

Companion PR

This unblocks CardputerZero/emulator#2 — once this merges, that PR drops the corresponding workaround in cmake/patches/apply_vendor_workarounds.cmake and bumps the launcher submodule.