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/crates/warzone-protocol/src/message.rs

@@ -101,4 +101,34 @@ pub enum WireMessage {
         chain_key: [u8; 32],
         generation: u32,
     },
+    /// Call signaling: SDP offers/answers, ICE candidates, call control.
+    /// Routed through featherChat's E2E encrypted channel for WarzonePhone integration.
+    CallSignal {
+        id: String,
+        sender_fingerprint: String,
+        signal_type: CallSignalType,
+        /// SDP offer/answer body, ICE candidate, or empty for hangup/reject.
+        payload: String,
+        /// Target peer (for 1:1) or group/room name (for group calls).
+        target: String,
+    },
+}
+
+/// Call signaling types for WarzonePhone integration.
+#[derive(Clone, Debug, Serialize, Deserialize)]
+pub enum CallSignalType {
+    /// Initiate a call (contains SDP offer or WZP connection params).
+    Offer,
+    /// Accept a call (contains SDP answer or WZP connection params).
+    Answer,
+    /// ICE candidate for NAT traversal.
+    IceCandidate,
+    /// Hang up / end call.
+    Hangup,
+    /// Reject incoming call.
+    Reject,
+    /// Call is ringing on the other side.
+    Ringing,
+    /// Peer is busy.
+    Busy,
 }