feat: add webhook notification system with Settings UI (REMOTE-03)

Webhook module with HTTP delivery, HMAC-SHA256 signing, and event
filtering. RPC handlers for get-config, configure, and test endpoints.
Settings page gains webhook configuration section with URL, secret,
event toggles, and test button.

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

core/archipelago/Cargo.toml

@@ -42,11 +42,13 @@ archipelago-parmanode = { path = "../parmanode" }
 # Authentication
 bcrypt = "0.15"
 sha2 = "0.10"
+hmac = "0.12"
 uuid = { version = "1.0", features = ["v4"] }
 regex = "1.10"
 
-# Node identity (Ed25519)
+# Node identity (Ed25519 + X25519 key agreement)
 ed25519-dalek = { version = "2.1", features = ["rand_core"] }
+curve25519-dalek = "4"
 rand = "0.8"
 hex = "0.4"
 bs58 = "0.5"
@@ -57,7 +59,8 @@ toml = "0.8"
 serde_yaml = "0.9"
 
 # HTTP client (for LND REST proxy, Tor SOCKS for peer messaging)
-reqwest = { version = "0.11", features = ["json", "socks"] }
+# Uses rustls-tls for cross-compilation (no OpenSSL dependency)
+reqwest = { version = "0.11", default-features = false, features = ["json", "socks", "rustls-tls"] }
 
 # Nostr (node discovery)
 nostr-sdk = "0.44"
@@ -67,6 +70,10 @@ argon2 = "0.5"
 chacha20poly1305 = "0.10"
 base64 = "0.21"
 
+# Full system backup (tar archive + gzip compression)
+tar = "0.4"
+flate2 = "1.0"
+
 # TOTP 2FA
 totp-rs = { version = "5.7", features = ["otpauth", "gen_secret"] }
 qrcode = "0.14"