fix：fix UserChoice Hash algorithm

[k1988]

detail: The original code used the 7D60 token-encoding pipeline for BOTH UserChoiceLatest and UserChoice registry keys. But
SFTA.ps1 implements UserChoice with a simpler algorithm (no token encoding, different canonical input format,
minute-rounded timestamp).

Files modified

HashCommon.h — Added FILETIME last_write_raw to AssocContext + ComputeHashUserChoice() declaration.

HashCodec.cpp — Added ComputeHashUserChoice() implementing the SFTA.ps1 algorithm:

• UTF-16LE encode canonical input + null terminator
• MD5 directly on raw bytes (no token encoding)
• Same MixA/MixB/XOR/Base64 core (reuses existing functions, same seeds)

RegistryContext.cpp — Three additions:

1. kUserExperience constant matching SFTA.ps1's experience string
2. FormatTimestampHexMinuteRounded() — rounds FILETIME to minute precision (SFTA.ps1 Get-HexDateTime rounds seconds to 0)
3. BuildCanonicalInputUserChoice() — fixed-format canonical string: assoc + sid + progid + timestamp + experience
4. VerifyCurrentAssociation() now branches: UserChoiceLatest → 7D60 pipeline, UserChoice → SFTA.ps1-compatible algorithm
5. LoadAssociationContext() stores raw FILETIME and uses minute-rounded timestamp for UserChoice key