COLDCARD firmware

This update fixes how the COLDCARD hardware wallet's random-number generator (RNG) handles rare hardware faults. Previously, the device could silently continue using weak or repeated random numbers if the RNG reported a seed error. Now it detects those error flags, tries a safe recovery a few times, and if the problem persists it stops with an error instead of producing bad randomness. Two keyboard drivers were also updated so a temporary RNG failure does not lock the user out before login.

This commit changes how the COLDCARD hardware wallet's random-number generator (RNG) recovers from a rare 'seed error' condition. The manufacturer is now following an STMicroelectronics guideline to throw away the first 12 random numbers after clearing the error, because those values could be left over from before the error and might be predictable. Random numbers are critical for creating private keys and transaction signatures, so using weak or stale randomness could in theory weaken security. The patch is defensive and does not by itself prove an attack exists.

This commit only adds explanatory comments to two source files about why the COLDCARD firmware ignores certain hardware random-number-generator clock-error flags. It does not change any code behavior. The comments cite ST documentation saying these clock errors do not affect the quality of random numbers and that a dead clock is still caught by a data-ready timeout. There is no security-relevant code change.

This commit fixes a critical random-number bug in COLDCARD hardware wallets. The device was accidentally using a weak, software-based fallback random generator instead of its secure hardware one when creating Bitcoin seed phrases. Because the fallback generator had very little real randomness, attackers who captured a public transaction or signature could potentially figure out the wallet's private keys and steal funds. The patch forces the build to use the hardware random source and adds a build-time check to make sure the weak fallback is never linked in again. Coinkite issued an emergency hotfix and warned users to move funds from wallets created with affected firmware.