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>

src/NexusReader.UI.Shared/Components/Organisms/ContextualRecommendationsWidget.razor.css

@@ -5,6 +5,7 @@
 .recommendations-panel {
     width: 100%;
     padding: 1.75rem;
+    margin-top: 2.5rem;
     background: var(--nexus-surface, #1a1a1e);
     border: 1px solid var(--nexus-border, rgba(255, 255, 255, 0.05));
     border-radius: 12px;