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.lock

@@ -2789,7 +2789,7 @@ dependencies = [
 
 [[package]]
 name = "warzone-client"
-version = "0.0.19"
+version = "0.0.20"
 dependencies = [
  "anyhow",
  "argon2",
@@ -2822,7 +2822,7 @@ dependencies = [
 
 [[package]]
 name = "warzone-mule"
-version = "0.0.19"
+version = "0.0.20"
 dependencies = [
  "anyhow",
  "clap",
@@ -2831,7 +2831,7 @@ dependencies = [
 
 [[package]]
 name = "warzone-protocol"
-version = "0.0.19"
+version = "0.0.20"
 dependencies = [
  "base64",
  "bincode",
@@ -2856,7 +2856,7 @@ dependencies = [
 
 [[package]]
 name = "warzone-server"
-version = "0.0.19"
+version = "0.0.20"
 dependencies = [
  "anyhow",
  "axum",
@@ -2883,7 +2883,7 @@ dependencies = [
 
 [[package]]
 name = "warzone-wasm"
-version = "0.0.19"
+version = "0.0.20"
 dependencies = [
  "base64",
  "bincode",