L-3: getMatches() returns stale entries after profile burn/block

Summary

matches[user].push(...) entries are never removed when a profile is burned (burnProfile) or admin-blocked (blockProfile). A matched user whose profile no longer exists still appears in the partner's match list.

PoC (Foundry, PASS)

test_L3_staleMatchesAfterBurn: Alice/Bob match, owner calls blockProfile(bob); asserts Alice's getMatches() still returns Bob while profileToToken(bob) == 0. PASS.

Recommended mitigation

Tombstone matches on burn/block, or have getMatches filter by live profileToToken.