Effective config: auto-revert flag when toggled to original; fix stale cache after restore

- Flag options: when user toggles value back to original, clear pending change (same as revert button); trigger revert immediately on change so UI updates without blur
- UiContext: add RevertFieldAsync so section can revert a field and refresh; section wires it to Session.RevertChange + StateHasChanged
- RestoreAsync: call config cache Invalidate() after File.Copy so next read sees restored file (fixes validate-fail → restore showing pre-restore data)

src/DnsmasqWebUI/Components/EffectiveConfig/Composition/EffectiveConfigSection.razor

@@ -68,7 +68,8 @@
             },
             ActivateFieldAsync = fieldKey => { ActivateField(fieldKey); return Task.CompletedTask; },
             DeactivateFieldAsync = () => { Session.DeactivateField(); return InvokeAsync(StateHasChanged); },
-            CommitFieldAsync = args => { HandleFieldEditCommitted(args); return Task.CompletedTask; }
+            CommitFieldAsync = args => { HandleFieldEditCommitted(args); return Task.CompletedTask; },
+            RevertFieldAsync = (sectionId, optionName) => { Session.RevertChange(sectionId, optionName); return InvokeAsync(StateHasChanged); }
         };
     }
 

src/DnsmasqWebUI/Components/EffectiveConfig/Fields/EffectiveConfigFieldDisplay.razor

@@ -171,6 +171,8 @@ else
     private void HandleValueChanged(object? value)
     {
         _draftValue = value;
+        if (_hasPendingChange && ValuesEqual(_valueAtActivation, value))
+            _ = InvokeAsync(CommitIfChangedAsync);
     }
 
     private async Task OnBlur(FocusEventArgs _)
@@ -182,8 +184,13 @@ else
     private async Task<bool> CommitIfChangedAsync()
     {
         var newValue = _draftValue ?? _effectiveValue;
-        if (!ValuesEqual(_valueAtActivation, newValue))
+        if (ValuesEqual(_valueAtActivation, newValue))
         {
+            _draftValue = null;
+            if (_hasPendingChange && Ui?.RevertFieldAsync != null)
+                await Ui.RevertFieldAsync(Descriptor.SectionId, Descriptor.OptionName);
+            return true;
+        }
         var validationError = ValidateDraftValue(newValue);
         if (validationError != null)
         {
@@ -201,7 +208,6 @@ else
         var args = new EffectiveConfigEditCommittedArgs(Descriptor.SectionId, Descriptor.OptionName, _valueAtActivation, valueToCommit, source?.FilePath);
         if (Ui != null)
             await Ui.CommitFieldAsync(args);
-        }
         _draftValue = null;
         return true;
     }

src/DnsmasqWebUI/Infrastructure/Services/EffectiveConfig/EffectiveConfigSaveService.cs

@@ -11,6 +11,7 @@ public sealed class EffectiveConfigSaveService : IEffectiveConfigSaveService
 {
     private readonly IDnsmasqConfigSetService _configSetService;
     private readonly IDnsmasqConfigService _configService;
+    private readonly IConfigSetCache _configSetCache;
     private readonly IConfigValidationService _validationService;
     private readonly IReloadService _reloadService;
     private readonly ILogger<EffectiveConfigSaveService> _logger;
@@ -18,12 +19,14 @@ public sealed class EffectiveConfigSaveService : IEffectiveConfigSaveService
     public EffectiveConfigSaveService(
         IDnsmasqConfigSetService configSetService,
         IDnsmasqConfigService configService,
+        IConfigSetCache configSetCache,
         IConfigValidationService validationService,
         IReloadService reloadService,
         ILogger<EffectiveConfigSaveService> logger)
     {
         _configSetService = configSetService;
         _configService = configService;
+        _configSetCache = configSetCache;
         _validationService = validationService;
         _reloadService = reloadService;
         _logger = logger;
@@ -139,6 +142,7 @@ public sealed class EffectiveConfigSaveService : IEffectiveConfigSaveService
 
         var managedPath = set.ManagedFilePath!;
         File.Copy(backupPath, managedPath, overwrite: true);
+        _configSetCache.Invalidate();
         _logger.LogInformation("Restored managed config from backup: {BackupPath}", backupPath);
 
         var restartResult = await _reloadService.ReloadAsync(ct);

src/DnsmasqWebUI/Models/Dnsmasq/EffectiveConfig/EffectiveConfigUiContext.cs

@@ -12,4 +12,6 @@ public sealed class EffectiveConfigUiContext
     public required Func<string, Task> ActivateFieldAsync { get; init; }
     public required Func<Task> DeactivateFieldAsync { get; init; }
     public required Func<EffectiveConfigEditCommittedArgs, Task> CommitFieldAsync { get; init; }
+    /// <summary>Revert a pending change for the given field and refresh the section (e.g. when user toggles a flag back to its original value).</summary>
+    public Func<string, string, Task>? RevertFieldAsync { get; init; }
 }