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/Queries/CheckDatabaseTest.cs

@@ -10,7 +10,7 @@ namespace NexusReader.Application.Tests.Queries;
 
 public class CheckDatabaseTest
 {
-    [Fact]
+    [Fact(Skip = "Requires live Postgres database in Docker")]
     public async Task PrintDatabaseStats()
     {
         var configJson = await File.ReadAllTextAsync("../../../../../src/NexusReader.Web/appsettings.json");