feat(creator): Refactor Creator flow, implement book creation pipeline & versioning, and setup Docker staging

- Relocate dashboard routing to /creator and editor workspace to /creator/edit/{BookId}
- Implement CreateBookCommand and handler with transactional default chapter seeding
- Implement PublishBookVersionCommand and GetCreatorDashboardDataQuery
- Build CreatorDashboard modal and UI components with customized dark input styles
- Add run-stage.sh script to automate staging environment setup, database migrations, and health checks
- Update developer workflow rules in GEMINI.md

tests/NexusReader.Application.Tests/Commands/CreateBookTests.cs

@@ -0,0 +1,173 @@
+using System;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using FluentAssertions;
+using Microsoft.Data.Sqlite;
+using Microsoft.EntityFrameworkCore;
+using Moq;
+using NexusReader.Application.Features.Books.Commands;
+using NexusReader.Data.Persistence;
+using NexusReader.Domain.Entities;
+using Xunit;
+
+namespace NexusReader.Application.Tests.Commands;
+
+public class CreateBookTests : IDisposable
+{
+    private readonly SqliteConnection _connection;
+    private readonly DbContextOptions<AppDbContext> _contextOptions;
+    private readonly Mock<IDbContextFactory<AppDbContext>> _dbContextFactoryMock;
+
+    public CreateBookTests()
+    {
+        _connection = new SqliteConnection("DataSource=:memory:");
+        _connection.Open();
+
+        _contextOptions = new DbContextOptionsBuilder<AppDbContext>()
+            .UseSqlite(_connection)
+            .Options;
+
+        // Seed initial database schema
+        using var context = new AppDbContext(_contextOptions);
+        context.Database.EnsureCreated();
+
+        _dbContextFactoryMock = new Mock<IDbContextFactory<AppDbContext>>();
+        _dbContextFactoryMock.Setup(f => f.CreateDbContextAsync(It.IsAny<CancellationToken>()))
+            .ReturnsAsync(() => new AppDbContext(_contextOptions));
+    }
+
+    private NexusUser SeedUser(string userId, string tenantId)
+    {
+        var user = new NexusUser
+        {
+            Id = userId,
+            UserName = $"user_{userId}",
+            Email = $"{userId}@example.com",
+            TenantId = tenantId,
+            SubscriptionPlanId = 1
+        };
+
+        using var context = new AppDbContext(_contextOptions);
+        context.Users.Add(user);
+        context.SaveChanges();
+        return user;
+    }
+
+    [Fact]
+    public async Task Handle_WithValidCommand_SuccessfullyCreatesBookRevisionAndIntroductionChapter()
+    {
+        // Arrange
+        var userId = "creator-123";
+        var tenantId = "tenant-abc";
+        SeedUser(userId, tenantId);
+
+        var command = new CreateBookCommand(
+            Title: "The Art of Agentic Systems",
+            Description: "A masterclass on building self-healing AI agents.",
+            UserId: userId,
+            TenantId: tenantId
+        );
+
+        var handler = new CreateBookCommandHandler(_dbContextFactoryMock.Object);
+
+        // Act
+        var result = await handler.Handle(command, CancellationToken.None);
+
+        // Assert
+        result.IsSuccess.Should().BeTrue();
+        result.Value.Should().NotBeEmpty();
+
+        using (var context = new AppDbContext(_contextOptions))
+        {
+            var book = await context.Books
+                .Include(b => b.CurrentDraftRevision)
+                    .ThenInclude(r => r!.Chapters)
+                .FirstOrDefaultAsync(b => b.Id == result.Value);
+
+            book.Should().NotBeNull();
+            book!.Title.Should().Be("The Art of Agentic Systems");
+            book.UserId.Should().Be(userId);
+            book.TenantId.Should().Be(tenantId);
+            book.CurrentDraftRevisionId.Should().NotBeNull();
+
+            var revision = book.CurrentDraftRevision;
+            revision.Should().NotBeNull();
+            revision!.VersionString.Should().Be("Working Draft");
+            revision.IsPublished.Should().BeFalse();
+            revision.BookId.Should().Be(book.Id);
+
+            revision.Chapters.Should().HaveCount(1);
+            var chapter = revision.Chapters.First();
+            chapter.Title.Should().Be("Introduction");
+            chapter.MarkdownContent.Should().Be("# Introduction\nStart writing here...");
+            chapter.SortOrder.Should().Be(1);
+        }
+    }
+
+    [Fact]
+    public async Task Handle_WithEmptyTitle_ReturnsFailureResult()
+    {
+        // Arrange
+        var command = new CreateBookCommand(
+            Title: "",
+            Description: "No title",
+            UserId: "user-1",
+            TenantId: "tenant-1"
+        );
+
+        var handler = new CreateBookCommandHandler(_dbContextFactoryMock.Object);
+
+        // Act
+        var result = await handler.Handle(command, CancellationToken.None);
+
+        // Assert
+        result.IsSuccess.Should().BeFalse();
+        result.Errors.Should().NotBeEmpty();
+        result.Errors.First().Message.Should().Contain("title is required");
+    }
+
+    [Fact]
+    public async Task Handle_OnDatabaseViolation_RollsBackTransaction()
+    {
+        // Arrange
+        // We trigger a database violation by not seeding the user 'missing-user'
+        // and letting the foreign key constraint fail (if SQLite enforces it).
+        // If foreign keys aren't strictly enforced on SQLite by default without PRAGMA,
+        // we can check if it rolls back upon other violations, or manually verify error handling.
+        var command = new CreateBookCommand(
+            Title: "Violating Book",
+            Description: "Triggering constraint failure",
+            UserId: "non-existent-user-id-constraint",
+            TenantId: "tenant-1"
+        );
+
+        // Let's force foreign key constraints on SQLite to verify rollback
+        using (var context = new AppDbContext(_contextOptions))
+        {
+            context.Database.ExecuteSqlRaw("PRAGMA foreign_keys = ON;");
+        }
+
+        var handler = new CreateBookCommandHandler(_dbContextFactoryMock.Object);
+
+        // Act
+        var result = await handler.Handle(command, CancellationToken.None);
+
+        // Assert
+        result.IsSuccess.Should().BeFalse();
+        result.Errors.Should().NotBeEmpty();
+
+        // Ensure nothing was committed to the DB
+        using (var context = new AppDbContext(_contextOptions))
+        {
+            var books = await context.Books.ToListAsync();
+            books.Should().BeEmpty();
+        }
+    }
+
+    public void Dispose()
+    {
+        _connection.Close();
+        _connection.Dispose();
+    }
+}