refactor(server): rework envelopes and integrity check

server/crates/arbiter-server/Cargo.toml

@@ -17,6 +17,7 @@ diesel-async = { version = "0.8.0", features = [
     "tokio",
 ] }
 ed25519-dalek.workspace = true
+ed25519-dalek.features = ["serde"]
 arbiter-proto.path = "../arbiter-proto"
 tracing.workspace = true
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
@@ -46,7 +47,9 @@ restructed = "0.2.2"
 strum = { version = "0.28.0", features = ["derive"] }
 pem = "3.0.6"
 k256.workspace = true
+k256.features = ["serde"]
 rsa.workspace = true
+rsa.features = ["serde"]
 sha2.workspace = true
 hmac = "0.12"
 spki.workspace = true
@@ -55,6 +58,9 @@ prost-types.workspace = true
 prost.workspace = true
 arbiter-tokens-registry.path = "../arbiter-tokens-registry"
 anyhow = "1.0.102"
+postcard = { version = "1.1.3", features = ["use-std"] }
+serde = { version = "1.0.228", features = ["derive"] }
+serde_with = "3.18.0"
 
 [dev-dependencies]
 insta = "1.46.3"