feat: landing page + logo, dev-mode banner + sync cap, non-blocking sync with progress splash

src/InboxIntel.Infrastructure/Sync/SyncQueue.cs

@@ -0,0 +1,18 @@
+using System.Threading.Channels;
+using InboxIntel.Application.Abstractions;
+
+namespace InboxIntel.Infrastructure.Sync;
+
+/// <summary>
+/// In-process unbounded queue of sync jobs, backed by a Channel. Registered as
+/// a singleton; the controller writes, <see cref="SyncQueueWorker"/> reads.
+/// </summary>
+public sealed class SyncQueue : ISyncQueue
+{
+    private readonly Channel<(Guid UserId, bool Full)> _channel =
+        Channel.CreateUnbounded<(Guid, bool)>(new UnboundedChannelOptions { SingleReader = true });
+
+    public void Enqueue(Guid userId, bool fullSync) => _channel.Writer.TryWrite((userId, fullSync));
+
+    public ChannelReader<(Guid UserId, bool Full)> Reader => _channel.Reader;
+}

src/InboxIntel.Infrastructure/Sync/SyncQueueWorker.cs

@@ -0,0 +1,44 @@
+using InboxIntel.Application.Abstractions;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+
+namespace InboxIntel.Infrastructure.Sync;
+
+/// <summary>
+/// Drains the <see cref="SyncQueue"/> and runs each sync in its own DI scope,
+/// then refreshes analytics aggregates. Keeps sync work off the request thread.
+/// </summary>
+public class SyncQueueWorker : BackgroundService
+{
+    private readonly SyncQueue _queue;
+    private readonly IServiceScopeFactory _scopeFactory;
+    private readonly ILogger<SyncQueueWorker> _logger;
+
+    public SyncQueueWorker(SyncQueue queue, IServiceScopeFactory scopeFactory, ILogger<SyncQueueWorker> logger)
+    {
+        _queue = queue;
+        _scopeFactory = scopeFactory;
+        _logger = logger;
+    }
+
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        await foreach (var (userId, full) in _queue.Reader.ReadAllAsync(stoppingToken))
+        {
+            using var scope = _scopeFactory.CreateScope();
+            var sync = scope.ServiceProvider.GetRequiredService<ISyncService>();
+            var analytics = scope.ServiceProvider.GetRequiredService<IAnalyticsService>();
+            try
+            {
+                if (full) await sync.RunFullSyncAsync(userId, stoppingToken);
+                else await sync.RunIncrementalSyncAsync(userId, stoppingToken);
+                await analytics.RefreshAggregatesAsync(userId, stoppingToken);
+            }
+            catch (Exception ex)
+            {
+                _logger.LogError(ex, "Queued sync failed for user {UserId}", userId);
+            }
+        }
+    }
+}

src/InboxIntel.Infrastructure/Sync/SyncService.cs

@@ -1,10 +1,13 @@
 using InboxIntel.Application.Abstractions;
+using InboxIntel.Application.DTOs;
 using InboxIntel.Domain.Entities;
 using InboxIntel.Domain.Enums;
+using InboxIntel.Infrastructure.Configuration;
 using InboxIntel.Infrastructure.Gmail;
 using InboxIntel.Infrastructure.Persistence;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
 
 namespace InboxIntel.Infrastructure.Sync;
 
@@ -19,17 +22,46 @@ public class SyncService : ISyncService
     private readonly AppDbContext _db;
     private readonly IGmailService _gmail;
     private readonly ILogger<SyncService> _logger;
+    private readonly GmailSyncOptions _options;
+    private readonly ISyncQueue _queue;
 
-    public SyncService(AppDbContext db, IGmailService gmail, ILogger<SyncService> logger)
+    public SyncService(AppDbContext db, IGmailService gmail, ILogger<SyncService> logger, IOptions<GmailSyncOptions> options, ISyncQueue queue)
     {
         _db = db;
         _gmail = gmail;
         _logger = logger;
+        _options = options.Value;
+        _queue = queue;
+    }
+
+    public async Task QueueSyncAsync(Guid userId, bool fullSync, CancellationToken ct = default)
+    {
+        // Flip to Running synchronously so the UI splash shows immediately,
+        // then hand the actual work to the background worker.
+        var state = await GetOrCreateStateAsync(userId, ct);
+        state.Status = SyncStatus.Running;
+        state.LastSyncType = fullSync ? SyncType.Full : SyncType.Incremental;
+        state.StartedUtc = DateTimeOffset.UtcNow;
+        state.LastError = null;
+        if (fullSync) state.MessagesProcessed = 0;
+        await _db.SaveChangesAsync(ct);
+        _queue.Enqueue(userId, fullSync);
     }
 
     public async Task<SyncStatus> GetStatusAsync(Guid userId, CancellationToken ct = default)
         => (await GetOrCreateStateAsync(userId, ct)).Status;
 
+    public async Task<SyncProgressDto> GetProgressAsync(Guid userId, CancellationToken ct = default)
+    {
+        var s = await GetOrCreateStateAsync(userId, ct);
+        var total = _options.MaxMessages > 0
+            ? Math.Min(s.TotalMessagesEstimate == 0 ? _options.MaxMessages : s.TotalMessagesEstimate, _options.MaxMessages)
+            : s.TotalMessagesEstimate;
+        return new SyncProgressDto(
+            s.Status.ToString(), s.MessagesProcessed, total,
+            s.Status == SyncStatus.Running, s.LastSuccessfulSyncUtc, s.LastError);
+    }
+
     public async Task RunFullSyncAsync(Guid userId, CancellationToken ct = default)
     {
         var state = await GetOrCreateStateAsync(userId, ct);
@@ -43,12 +75,21 @@ public class SyncService : ISyncService
         {
             await SyncLabelsAsync(userId, ct);
 
+            // Dev cap: stop after MaxMessages (most recent first). 0 = unlimited.
+            var maxMessages = _options.MaxMessages;
+            var capReached = false;
+
             string? pageToken = state.ResumePageToken; // resume support
             do
             {
                 var page = await _gmail.ListMessageIdsAsync(userId, pageToken, ct);
                 foreach (var messageId in page.MessageIds)
                 {
+                    if (maxMessages > 0 && state.MessagesProcessed >= maxMessages)
+                    {
+                        capReached = true;
+                        break;
+                    }
                     if (await _db.Emails.AnyAsync(e => e.UserId == userId && e.GmailMessageId == messageId, ct))
                         continue;
                     var detail = await _gmail.GetMessageAsync(userId, messageId, ct);
@@ -58,10 +99,12 @@ public class SyncService : ISyncService
 
                 pageToken = page.NextPageToken;
                 state.ResumePageToken = pageToken;       // checkpoint
-                state.TotalMessagesEstimate = page.ResultSizeEstimate;
+                state.TotalMessagesEstimate = maxMessages > 0
+                    ? Math.Min(page.ResultSizeEstimate, maxMessages)
+                    : page.ResultSizeEstimate;
                 await _db.SaveChangesAsync(ct);
             }
-            while (pageToken is not null && !ct.IsCancellationRequested);
+            while (pageToken is not null && !capReached && !ct.IsCancellationRequested);
 
             state.LastHistoryId = await _gmail.GetProfileHistoryIdAsync(userId, ct);
             state.ResumePageToken = null;