fix: bump peerclaw-core to v0.7.0, update Sign/SignEnvelope call sites

The code already expected identity.Sign to return (string, error) and
identity.SignEnvelope to return error, but go.mod pinned v0.6.2 where
Sign returned only string and SignEnvelope returned nothing. Bump to
v0.7.0 which adds nil-key guards and error returns to both functions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: gcmsg

go.mod

@@ -8,7 +8,7 @@ require (
 	github.com/coder/websocket v1.8.14
 	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.4.0
 	github.com/google/uuid v1.6.0
-	github.com/peerclaw/peerclaw-core v0.6.2
+	github.com/peerclaw/peerclaw-core v0.7.0
 	github.com/pion/webrtc/v4 v4.1.2
 	golang.org/x/crypto v0.48.0
 )

go.sum

@@ -32,12 +32,8 @@ github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd h1:TRLaZ9cD/w
 github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd/go.mod h1:6dJC0mAP4ikYIbvyc7fijjWJddQyLn8Ig3JB5CqoB9Q=
 github.com/modern-go/reflect2 v1.0.2 h1:xBagoLtFs94CBntxluKeaWgTMpvLxC4ur3nMaC9Gz0M=
 github.com/modern-go/reflect2 v1.0.2/go.mod h1:yWuevngMOJpCy52FWWMvUC8ws7m/LJsjYzDa0/r8luk=
-github.com/peerclaw/peerclaw-core v0.6.0 h1:2Ng1dRgKo+Kg1/R9ybAWrIxX/Otc3veemQe39hEKJy0=
-github.com/peerclaw/peerclaw-core v0.6.0/go.mod h1:nlxhZV5ClCDDAh11ubrTLFluae1fK7bLj3uyUk/Gc4A=
-github.com/peerclaw/peerclaw-core v0.6.1 h1:xacM1gXa0ypFC31nNCvqY+9dr2s4xxQb/mWhybMIgP8=
-github.com/peerclaw/peerclaw-core v0.6.1/go.mod h1:nlxhZV5ClCDDAh11ubrTLFluae1fK7bLj3uyUk/Gc4A=
-github.com/peerclaw/peerclaw-core v0.6.2 h1:NIxTcOisypXJ+CYJunCIUkKHpFcP9QeJrMbqn+sokuU=
-github.com/peerclaw/peerclaw-core v0.6.2/go.mod h1:nlxhZV5ClCDDAh11ubrTLFluae1fK7bLj3uyUk/Gc4A=
+github.com/peerclaw/peerclaw-core v0.7.0 h1:x7Z4QWRExGv0Fcv2WnD45JTer/Fktsgpt8IAx5LRwLI=
+github.com/peerclaw/peerclaw-core v0.7.0/go.mod h1:nlxhZV5ClCDDAh11ubrTLFluae1fK7bLj3uyUk/Gc4A=
 github.com/pion/datachannel v1.5.10 h1:ly0Q26K1i6ZkGf42W7D4hQYR90pZwzFOjTq5AuCKk4o=
 github.com/pion/datachannel v1.5.10/go.mod h1:p/jJfC9arb29W7WrxyKbepTU20CFgyx5oLo8Rs4Py/M=
 github.com/pion/dtls/v3 v3.0.6 h1:7Hkd8WhAJNbRgq9RgdNh1aaWlZlGpYTzdqjy9x9sK2E=