Prevent malicious peers from forging events attributed to users on other
instances. Every relay event processor now verifies the acting user's
homeInstance (from payload) matches X-Federation-Origin (from HMAC-verified
header) via verifyAttribution(), normalized to bare domain.
- Add verifyAttribution() helper using extractDomain normalization
- Guard all 13 event processors before any user resolution or DB writes
- Add homeInstance to FederationRelayReaction type + outbound payloads
- Replace unnormalized string equality in friend handlers
- Log mismatched values on rejection for debugging
Jannis Braun
720a5de945