feat(center): POST /auth/resolve-names

Resolve display names/emails to userIds within a guild node's active
members (api-key auth). Used by guild for <@user.name:NAME> translation.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/auth/auth.service.ts

@@ -240,6 +240,33 @@ export class AuthService {
       .filter((x) => !!x.email);
   }
 
+  // Resolve display names (or emails) to userIds, scoped to a guild node's
+  // active members. Called by guild nodes (api-key auth). Unresolved names
+  // are omitted from the result.
+  async resolveNames(
+    guildNodeId: string,
+    names: string[],
+  ): Promise<{ resolved: Record<string, string> }> {
+    const wanted = [...new Set(names.map((n) => String(n ?? '').trim()).filter(Boolean))];
+    if (!guildNodeId || !wanted.length) return { resolved: {} };
+
+    const members = await this.guildUserRepo.find({ where: { guildNodeId, status: 'active' } });
+    const userIds = [...new Set(members.map((m) => m.userId))];
+    if (!userIds.length) return { resolved: {} };
+
+    const users = await this.userRepo
+      .createQueryBuilder('u')
+      .where('u.id IN (:...userIds)', { userIds })
+      .getMany();
+
+    const resolved: Record<string, string> = {};
+    for (const name of wanted) {
+      const hit = users.find((u) => u.name === name) ?? users.find((u) => u.email === name);
+      if (hit) resolved[name] = hit.id;
+    }
+    return { resolved };
+  }
+
   verifyCenterAccessToken(accessToken: string): jwt.JwtPayload {
     try {
       const payload = jwt.verify(accessToken, process.env.FABRIC_BACKEND_CENTER_JWT_ACCESS_SECRET as string) as jwt.JwtPayload;