Add totp-gba

[dmang-dev]

Adds totp-gba to the GBA homebrew database.

A native ARM7TDMI TOTP (RFC 6238) authenticator — same protocol as Google Authenticator. Pure C, built with devkitARM + libtonc, MIT-licensed. Includes prebuilt ROM, five screenshots, and a complete game.json.

Highlights:

• Hardware RTC support via cart-edge Seiko S-3511A bit-banging (auto-detected, with software-VBlank fallback for carts without an RTC chip)
• Twelve color themes (Phosphor green, Amber CRT, Pip-Boy, Solarized, GB DMG, Atari 2600, GB Camera sepia, etc.)
• Persistent SRAM storage for up to 8 accounts
• OAM sprite cursor with bobbing animation
• APU sound effects on PSG channels 1+4
• Boot self-test logging via the mGBA debug-log register

Verified end-to-end on real RTC vectors and four hardcoded TOTP known-answer vectors. Repo includes a headless mGBA verification script for CI.