docs: complete XML doc coverage (returns, summaries, inheritdoc)

Resolve all 622 issues flagged by the enhanced CommentChecker: add missing
<returns> tags (incl. the standard phrasing on non-generic Task methods),
add missing <summary> tags, and replace misused/redundant <inheritdoc/> on
members that override or implement nothing with real documentation.
Documentation-only — no behavior change; solution builds clean.

src/ZB.MOM.WW.ScadaBridge.Security/ServiceCollectionExtensions.cs

@@ -33,6 +33,7 @@ public static class ServiceCollectionExtensions
     /// <c>IConfiguration</c>) and component libraries must not accept <c>IConfiguration</c>.
     /// </remarks>
     /// <param name="services">The service collection to register into.</param>
+    /// <returns>The same <paramref name="services"/> instance for chaining.</returns>
     public static IServiceCollection AddSecurity(this IServiceCollection services)
     {
         // Task 1.2 cutover: ScadaBridge's bespoke LdapAuthService was replaced by the
@@ -146,6 +147,7 @@ public static class ServiceCollectionExtensions
     /// Registers security-related Akka actors (placeholder for future actor registrations).
     /// </summary>
     /// <param name="services">The service collection to register into.</param>
+    /// <returns>The same <paramref name="services"/> instance for chaining.</returns>
     public static IServiceCollection AddSecurityActors(this IServiceCollection services)
     {
         // Phase 0: placeholder for Akka actor registration