Add live e2e tests for the nostr relay and NIP-05 server

tests/nostr_e2e.rs (run with --ignored):
- nip17_slatepack_roundtrip: Alice gift-wraps a slatepack payment DM with a
  subject to Bob over wss://nrelay.us-ea.st; Bob unwraps, the seal-author ==
  sender invariant holds, the slatepack and subject extract intact.
- nip05_registration_roundtrip: registers a fresh name on goblin.st with a
  real NIP-98 signature, resolves it back to the right pubkey, releases it.

Both pass against the live deployed infrastructure.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Cargo.toml

@@ -150,3 +150,10 @@ eframe = { version = "0.33.2", default-features = false, features = ["glow", "an
 
 [build-dependencies]
 built = "0.8.0"
+
+[dev-dependencies]
+nostr-sdk = { version = "0.44", features = ["nip06", "nip44", "nip49", "nip59", "nip98"] }
+tokio = { version = "1.49.0", features = ["full"] }
+base64 = "0.22"
+sha2 = "0.10"
+hex = "0.4"