Feature: RetroAchievements support

[aabrole]

Requested by u/Xion_Stellar and u/Am3n. From Feedback Round 1.

[aabrole]

Implemented in the unreleased test build: rcheevos v12.4.0 client in the engine, login card in settings (token kept after the first login), hardcore mode (disables fast-forward), unlock pop-ups on the main screen and an RA strip on the bottom screen.

Blocker: retroachievements.org links only one hash to game 1378 (b6947e630bcf9e68aa3cf998d89357ac). This port requires the USA rev 0 cartridge dump, whose canonical RA hash is e4d94ad05dd5490e73ae9cb0b21f0d6b (computed by rcheevos from header + ARM9 + ARM7 + icon block), so the game is not recognized. A request to link the rev 0 hash to game 1378 is needed on the RA side (game forum thread or the RA Discord hash-linking channel). No spoofing: sending a different hash would misreport the ROM and the set's memory addresses may differ between revisions.

[aabrole]

Shipped in v0.2.5: rcheevos client with login, hardcore, unlock pop-ups, an achievements browser in settings, and an optional bottom-screen strip. The rev 0 hash is still not linked on RA's side (see the hash note in the README and the opt-in switch); a hash-link request for e4d94ad05dd5490e73ae9cb0b21f0d6b to game 1378 is the clean fix.