feat(creator): overhaul Creator flow, editor duplication, and staging setup (#83)

This pull request completely overhauls the Creator editor flow, resolves the editor duplication race condition, aligns layout/styling themes in light and dark mode, and adds Docker staging setups.

### Key Changes
1. **Creator Flow Polish**: Redesigned the editor canvas to prevent double scrolling by delegating overflow to the editor canvas layer, updated styles to a premium aesthetic.
2. **Race Condition Prevention**: Resolved Crepe editor duplication when loading or switching chapters by tracking state via shared window maps (`window.editorCache`, `window.editorStates`) and checking `_lastInitializedEditorId` synchronously in Blazor.
3. **Theme Synchronization**: Integrated explicit theme initialization (`ThemeService.InitializeAsync()`) and anchored CSS isolation selectors to correctly sync with Light (Soft Sepia) and Deep Dark theme preferences.
4. **Staging Automation**: Created staging docker configurations with `--nexus-only` flag to allow iterative development without resetting PG/Neo4j database containers.

---------

Co-authored-by: Marek Jasiński <jasins.marek@gmail.com>
Reviewed-on: #83
Co-authored-by: Antigravity <antigravity@google.com>
Co-committed-by: Antigravity <antigravity@google.com>

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");