Add threat actor alias mappings for Chinese APT groups

[rolandpg]

Summary

Add alias mappings for Chinese APT groups to the alias resolver.

Context

The alias resolver maps alternate names to canonical threat actor names (e.g., Fancy Bear -> APT28). Chinese APT groups have many aliases across vendors that need mapping.

• File to edit: src/zettelforge/alias_resolver.py
• Tests: add to existing alias resolver tests

Acceptance Criteria

• Add at least 10 Chinese APT group alias mappings to the hardcoded aliases in alias_resolver.py
• Required mappings (at minimum):
  • Hafnium -> APT40 (also TEMP.Periscope, Leviathan)
  • Double Dragon -> APT41 (also Wicked Panda, Barium)
  • Stone Panda -> APT10 (also menuPass, Red Apollo)
  • Emissary Panda -> APT27 (also LuckyMouse, Iron Tiger)
  • Mustang Panda -> BRONZE PRESIDENT (also RedDelta, TA416)
• Aliases are case-insensitive (matching existing behavior)
• resolver.resolve("actor", "Hafnium") returns "apt40"
• At least 5 test cases covering the new mappings
• All existing tests pass

References

• MITRE ATT&CK Groups: https://attack.mitre.org/groups/
• Malpedia: https://malpedia.caad.fkie.fraunhofer.de/