fix(guild): emit is_friend / is_friend_apply in /guild/info members

GuildMemberInfo.cs:48-49 re-reads json["is_friend"] / json["is_friend_apply"]
UNGUARDED on top of the base-class UserInfoBase's guarded read. Our DTO had
them as int? with global WhenWritingNull → keys omitted → LitJson threw
KeyNotFoundException, crashing the client right after guild create.

Flip the fields to non-nullable int with JsonIgnoreCondition.Never so they
always ship, and wire a batched IFriendService.GetFriendRelationsAsync
lookup so the values are actually populated (single Contains-batched query
per relation table).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.EmulatedEntrypoint/Models/Dtos/Common/Guild/GuildMemberInfoDto.cs

@@ -30,13 +30,21 @@ public class GuildMemberInfoDto
     [JsonPropertyName("degree_id"), Key("degree_id"), JsonConverter(typeof(StringifiedIntConverter))]
     public int DegreeId { get; set; }
 
-    /// <summary>Optional — omit when the caller has no friend relationship with this member.</summary>
-    [JsonPropertyName("is_friend"), Key("is_friend")]
-    public int? IsFriend { get; set; }
+    /// <summary>
+    /// Client reads unconditionally in GuildMemberInfo.cs:48 (json["is_friend"].ToBoolean()) — always emit.
+    /// Base UserInfoBase guards this, but GuildMemberInfo re-reads it on top, unguarded. 0 = not a friend.
+    /// </summary>
+    [JsonPropertyName("is_friend"), Key("is_friend"),
+     JsonIgnore(Condition = JsonIgnoreCondition.Never)]
+    public int IsFriend { get; set; }
 
-    /// <summary>Optional — omit when no pending friend apply.</summary>
-    [JsonPropertyName("is_friend_apply"), Key("is_friend_apply")]
-    public int? IsFriendApply { get; set; }
+    /// <summary>
+    /// Client reads unconditionally in GuildMemberInfo.cs:49 (json["is_friend_apply"].ToBoolean()) — always emit.
+    /// 0 = no pending friend apply.
+    /// </summary>
+    [JsonPropertyName("is_friend_apply"), Key("is_friend_apply"),
+     JsonIgnore(Condition = JsonIgnoreCondition.Never)]
+    public int IsFriendApply { get; set; }
 
     /// <summary>
     /// Whether the official-account badge is shown for this member.