Add proposal conflict detector for review UI (#1022)

backend/src/Taskdeck.Api/Controllers/AutomationProposalsController.cs

@@ -28,6 +28,7 @@ public class AutomationProposalsController : AuthenticatedControllerBase
     private readonly IAutomationExecutorService _executorService;
     private readonly ISimilarDecisionService _similarDecisionService;
     private readonly BoardAuthorizationService _authorizationService;
+    private readonly IProposalConflictDetector _conflictDetector;
     private readonly ICardHistoryService _cardHistoryService;
     private readonly ISideEffectAnalyzer _sideEffectAnalyzer;
 
@@ -36,6 +37,7 @@ public AutomationProposalsController(
         IAutomationExecutorService executorService,
         ISimilarDecisionService similarDecisionService,
         BoardAuthorizationService authorizationService,
+        IProposalConflictDetector conflictDetector,
         ICardHistoryService cardHistoryService,
         ISideEffectAnalyzer sideEffectAnalyzer,
         IUserContext userContext) : base(userContext)
@@ -44,6 +46,7 @@ public AutomationProposalsController(
         _executorService = executorService;
         _similarDecisionService = similarDecisionService;
         _authorizationService = authorizationService;
+        _conflictDetector = conflictDetector;
         _cardHistoryService = cardHistoryService;
         _sideEffectAnalyzer = sideEffectAnalyzer;
     }
@@ -270,6 +273,23 @@ public async Task<IActionResult> DismissProposals(
             : result.ToErrorActionResult();
     }
 
+    /// <summary>
+    /// Gets tone-classified conflict/warning/status rows for a proposal.
+    /// </summary>
+    [HttpGet("{id}/conflicts")]
+    public async Task<IActionResult> GetProposalConflicts(Guid id, CancellationToken cancellationToken = default)
+    {
+        if (!TryGetCurrentUserId(out var callerUserId, out var errorResult))
+            return errorResult!;
+
+        var auth = await AuthorizeProposalAsync(id, callerUserId, requireWriteAccess: false, cancellationToken);
+        if (auth.ErrorResult is not null)
+            return auth.ErrorResult;
+
+        var result = await _conflictDetector.DetectConflictsAsync(id, callerUserId, cancellationToken);
+        return result.IsSuccess ? Ok(result.Value) : result.ToErrorActionResult();
+    }
+
     /// <summary>
     /// Gets the card history ledger for a proposal, showing all touches on affected cards.
     /// </summary>
@@ -304,7 +324,6 @@ public async Task<IActionResult> GetProposalSideEffects(Guid id, CancellationTok
         var result = await _sideEffectAnalyzer.AnalyzeAsync(id, cancellationToken);
         return result.IsSuccess ? Ok(result.Value) : result.ToErrorActionResult();
     }
-
     /// <summary>
     /// Gets a diff preview for a proposal showing what changes will be made.
     /// </summary>

backend/src/Taskdeck.Api/Extensions/ApplicationServiceRegistration.cs

@@ -47,6 +47,7 @@ public static IServiceCollection AddApplicationServices(this IServiceCollection
         services.AddScoped<HistoryService>();
         services.AddScoped<IHistoryService>(sp => sp.GetRequiredService<HistoryService>());
         services.AddScoped<IAutomationProposalService, AutomationProposalService>();
+        services.AddScoped<IProposalConflictDetector, ProposalConflictDetector>();
         services.AddScoped<ICardHistoryService, CardHistoryService>();
         services.AddScoped<ISideEffectAnalyzer, SideEffectAnalyzer>();
         services.AddScoped<IProposalRevisionService, ProposalRevisionService>();

backend/src/Taskdeck.Application/DTOs/ConflictRowDto.cs

@@ -0,0 +1,18 @@
+using Taskdeck.Domain.Entities;
+
+namespace Taskdeck.Application.DTOs;
+
+/// <summary>
+/// DTO for a single conflict/warning/status row returned by the conflict detector.
+/// </summary>
+public record ConflictRowDto(
+    ConflictTone Tone,
+    string Key,
+    string Value
+)
+{
+    public static ConflictRowDto FromDomain(ConflictRow row)
+    {
+        return new ConflictRowDto(row.Tone, row.Key, row.Value);
+    }
+}

backend/src/Taskdeck.Application/Interfaces/IAutomationProposalRepository.cs

@@ -20,6 +20,7 @@ public interface IAutomationProposalRepository : IRepository<AutomationProposal>
         string actionType,
         ProposalSourceType sourceType,
         CancellationToken cancellationToken = default);
+    Task<IReadOnlyList<AutomationProposal>> GetPendingByOperationTargetAsync(string targetType, string targetId, CancellationToken cancellationToken = default);
     Task<IEnumerable<AutomationProposal>> GetExpiredAsync(CancellationToken cancellationToken = default);
 
     /// <summary>

backend/src/Taskdeck.Application/Interfaces/ICardCommentRepository.cs

@@ -5,5 +5,6 @@ namespace Taskdeck.Application.Interfaces;
 public interface ICardCommentRepository : IRepository<CardComment>
 {
     Task<IEnumerable<CardComment>> GetByCardIdAsync(Guid cardId, CancellationToken cancellationToken = default);
+    Task<int> CountByCardIdAsync(Guid cardId, CancellationToken cancellationToken = default);
     Task<CardComment?> GetByIdWithMentionsAsync(Guid id, CancellationToken cancellationToken = default);
 }

backend/src/Taskdeck.Application/Services/IProposalConflictDetector.cs

@@ -0,0 +1,16 @@
+using Taskdeck.Application.DTOs;
+using Taskdeck.Domain.Common;
+
+namespace Taskdeck.Application.Services;
+
+/// <summary>
+/// Detects conflicts, warnings, and status signals for a proposal.
+/// Returns a tone-classified list of rows for the review UI.
+/// </summary>
+public interface IProposalConflictDetector
+{
+    Task<Result<IReadOnlyList<ConflictRowDto>>> DetectConflictsAsync(
+        Guid proposalId,
+        Guid userId,
+        CancellationToken cancellationToken = default);
+}