chore(auth): OtOpcUa unify dev LDAP base DN to dc=zb,dc=local (Task 1.6)

Replace all dev-directory dc=lmxopcua,dc=local references with dc=zb,dc=local
across LdapOptions default, integration harness overrides, docker-compose LDAP_ROOT,
AclEdit placeholder DN, and dev/smoke-test docs. CN/OU prefixes preserved.

src/Server/ZB.MOM.WW.OtOpcUa.AdminUI/Components/Pages/Clusters/AclEdit.razor

@@ -41,7 +41,7 @@ else
                     <div class="col-md-6 mb-3">
                         <label class="form-label" for="grp">LDAP group</label>
                         <InputText id="grp" @bind-Value="_form.LdapGroup" class="form-control form-control-sm mono"
-                                   placeholder="cn=Operators,ou=FleetAdmin,dc=lmxopcua,dc=local" />
+                                   placeholder="cn=Operators,ou=FleetAdmin,dc=zb,dc=local" />
                     </div>
                 </div>
                 <div class="row">

src/Server/ZB.MOM.WW.OtOpcUa.Security/Ldap/LdapOptions.cs

@@ -50,7 +50,7 @@ public sealed class LdapOptions
     public bool DevStubMode { get; set; }
 
     /// <summary>Gets or sets the LDAP search base DN.</summary>
-    public string SearchBase { get; set; } = "dc=lmxopcua,dc=local";
+    public string SearchBase { get; set; } = "dc=zb,dc=local";
 
     /// <summary>
     ///     Service-account DN used for search-then-bind. When empty, a direct-bind with