feat: implement missing NES mappers

[tuxnode]

Current Status

Implemented mappers:

• Mapper 0: NROM ✅
• Mapper 1: MMC1 ✅

Missing Mappers

Mapper	Name	Complexity	Games	Description
2	UxROM	Simple	Castlevania, Mega Man, Contra	PRG banking only, no CHR
3	CNROM	Simple	Double Dragon, Arkanoid	CHR banking, 32KB PRG
4	MMC3	Complex	Super Mario Bros. 3, Ninja Gaiden	PRG/CHR banking, IRQ, scanline counter
7	AxROM	Simple	Donkey Kong, Battletoads	32KB PRG switching, single-screen mirroring
9	MMC2	Complex	Punch-Out!!	PRG/CHR banking, latch-based CHR switching
11	Color Dreams	Simple	Crystal Mines, Zombie Nation	Simple PRG/CHR banking
66	GxROM	Simple	Gradius, Life Force	PRG/CHR banking
71	Camerica	Simple	Codemasters games	PRG banking, some with IRQ
163	NITRA	Complex	Some Chinese games	PRG/CHR banking, IRQ
195	WAIXING	Complex	Some Chinese games	PRG/CHR banking, battery-backed SRAM

Priority

1. MMC3 (4) - Most critical, used by many popular games
2. UxROM (2) - Very common, simple to implement
3. CNROM (3) - Common in action games
4. AxROM (7) - Used by several classic games

Notes

• Current implementation panics on unsupported mappers
• Consider adding a stub/warning mode for unsupported mappers instead of panic