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.CentralUI/Components/Pages/Design/TransportExport.razor.cs

@@ -182,6 +182,7 @@ public partial class TransportExport : ComponentBase
     /// importer enforces its own strength + lockout policies.
     /// </summary>
     /// <param name="s">The passphrase string to score.</param>
+    /// <returns>An integer from 0 (blank) to 4 (long, mixed case, digits, and symbols).</returns>
     internal static int PassphraseStrength(string s)
     {
         if (string.IsNullOrEmpty(s)) return 0;
@@ -261,6 +262,7 @@ public partial class TransportExport : ComponentBase
     /// knows exactly what an unencrypted export would leak.
     /// </summary>
     /// <param name="resolved">The resolved export closure whose secret fields are counted.</param>
+    /// <returns>The total number of non-empty secret fields across all external systems, SMTP configs, and database connections.</returns>
     internal static int CountSecrets(ResolvedExport resolved)
     {
         var count = 0;
@@ -367,6 +369,7 @@ public partial class TransportExport : ComponentBase
     /// </summary>
     /// <param name="sourceEnvironment">The environment label to embed in the filename (sanitised to filename-safe characters).</param>
     /// <param name="nowUtc">Timestamp to use for the datetime segment; defaults to <see cref="DateTimeOffset.UtcNow"/> when null.</param>
+    /// <returns>A filename of the form <c>scadabundle-{env}-{yyyy-MM-dd-HHmmss}.scadabundle</c>.</returns>
     internal static string BuildFilename(string sourceEnvironment, DateTimeOffset? nowUtc = null)
     {
         var safe = SanitizeForFilename(sourceEnvironment);
@@ -427,6 +430,7 @@ public partial class TransportExport : ComponentBase
     /// <param name="all">The full resolved list including both seed and auto-included items.</param>
     /// <param name="seed">The set of explicitly selected item ids.</param>
     /// <param name="idOf">Function that extracts the integer id from an item.</param>
+    /// <returns>Items from <paramref name="all"/> whose ids are not in <paramref name="seed"/> (auto-included dependencies).</returns>
     internal static IReadOnlyList<T> AutoIncluded<T>(IReadOnlyList<T> all, IReadOnlyCollection<int> seed, Func<T, int> idOf)
     {
         return all.Where(x => !seed.Contains(idOf(x))).ToList();