fix(#3344): type the roster entry's name as Ident, per review

A bare String in a crate whose whole suite types validated names as
hive_types::Ident, so a consumer had to re-derive at the boundary what every
sibling field gets checked for free.

Ident is strictly narrower than the store's charset — [a-z0-9-] against the
[A-Za-z0-9._-] the users database allows, because that file holds humans too.
Every agent name is a legal Ident by construction (creation parses one before
the job is queued), so the narrowing costs real agents nothing. What it does
mean is that a human hand-added to the agent group cannot be described as an
agent: the reader omits that row and logs it, rather than failing the whole
roster or quietly shrinking the answer.

The REQUEST keeps its String. That side carries what a caller asked for, and
validating it server-side is what lets a bad name be refused with a message
instead of failing to deserialise.

Cargo.lock

@@ -4544,6 +4544,7 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "axum",
+ "hive-types",
  "reqwest",
  "serde",
  "serde_json",
@@ -4558,6 +4559,7 @@ dependencies = [
 name = "swarm-authelia-bridge-sock"
 version = "0.1.0"
 dependencies = [
+ "hive-types",
  "serde",
  "serde_json",
 ]