v0.0.21: WZP integration groundwork — CallSignal + token validation

WZP-FC-1: CallSignal WireMessage variant
- CallSignalType enum: Offer, Answer, IceCandidate, Hangup, Reject, Ringing, Busy
- Routed through existing E2E encrypted channels
- Server dedup handles new variant
- TUI shows "📞 Call signal: Offer" etc
- CLI recv prints call signals

WZP-FC-4: Token validation endpoint
- POST /v1/auth/validate { "token": "..." }
- Returns: { "valid": true, "fingerprint": "...", "alias": "..." }
- WZP relay calls this to verify featherChat bearer tokens
- Resolves alias alongside fingerprint

These two unblock WZP integration tasks WZP-S-2 (accept FC tokens)
and WZP-S-3 (signaling bridge mode).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

warzone/Cargo.toml

@@ -9,7 +9,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.0.20"
+version = "0.0.21"
 edition = "2021"
 license = "MIT"
 rust-version = "1.75"