feat!: genesis-pinned operator set, server identity with an encrypted control link, key-less join codes; release key continuity

Join codes need no passkey touch and carry only public values (genesis
fingerprint, owner credentials, installer hashes). Nodes pin the genesis and
owners at enrollment and only follow passkey-signed operator set versions.
The panel's server key is listed in the set; pinned nodes require its
signature and run the control link under AES-256-GCM. Password sessions carry
no capabilities. The updater adopts a next_key from a signed manifest.

Bump version to 0.2.0. [CI SKIP]

backend/fleet/src/Fleet.Server.Enrollment/EnrollmentModels.cs

@@ -33,13 +33,6 @@ public sealed class EnrollRequest
     [JsonPropertyName("node_version")]
     public string NodeVersion { get; set; } = "";
 
-    /// <summary>带操作员委托的加入码要附上：用码的私钥签的绑定语句（节点的两把公钥和名字）和它的签名。</summary>
-    [JsonPropertyName("binding")]
-    public string? Binding { get; set; }
-
-    [JsonPropertyName("binding_signature")]
-    public string? BindingSignature { get; set; }
-
     [JsonPropertyName("meta")]
     public JsonElement? Meta { get; set; }
 }