feat: netplay support

[mohammadsyuhada]

Adds local two-player multiplayer to Minarch over WiFi — either over an existing network or an on-device hotspot (no router needed). A single in-game Netplay menu auto-selects the right link type for the loaded core.

What's included

• Netplay — RetroArch-style frame-synced input (input-latency buffering, stall handling) for frame-sync capable cores.
• GBA Link (gpSP) — bridges gpSP's RFU/Wireless Adapter to the network via the libretro netpacket interface (Pokémon trade, Union Room battles, etc.).
• GB Link (gambatte) — drives gambatte's built-in network serial via core options.

Key changes

• New Netplay menu item, shown only when the core supports a link type; Save/Load State blocked during a session.
• Core capability detection in Core_load + handling of RETRO_ENVIRONMENT_SET_NETPACKET_INTERFACE.
• UDP host discovery; WiFi creds saved/restored around hotspot sessions.
• New WiFi platform API: PLAT_wifiForgetPrefix / wifiEnableAll / wifiSelectOnly.
• gpSP patches (RFU disconnect fix + larger packet queue) — gpSP now pinned via gpsp_HASH.
• gambatte: HAVE_NETWORK=1 for ARM.

[johnnyq]

This is the missing piece thank you for this PR @mohammadsyuhada

Also can we get retro send as well as a Pull request