v2.0.0: Modularize project into single-responsibility packages

Replaced monolithic modules/ package with a clean architecture:

- core/       config.py, utils.py
- ai/         models.py (ResilientModel), setup.py (init_models)
- story/      planner.py, writer.py, editor.py, style_persona.py, bible_tracker.py
- marketing/  cover.py, blurb.py, fonts.py, assets.py
- export/     exporter.py
- web/        app.py (Flask factory), db.py, helpers.py, tasks.py, routes/{auth,project,run,persona,admin}.py
- cli/        engine.py (run_generation), wizard.py (BookWizard)

Flask routes split into 5 Blueprints; all templates updated with blueprint-
prefixed url_for() calls. Dockerfile and docker-compose updated to use
web.app entry point and new package paths.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

templates/base.html

@@ -28,7 +28,7 @@
     {% if session.get('original_admin_id') %}
     <div class="bg-danger text-white text-center py-2 shadow-sm" style="position: sticky; top: 0; z-index: 1050;">
         <strong><i class="fas fa-user-secret me-2"></i>Viewing site as {{ current_user.username }}</strong>
-        <a href="{{ url_for('stop_impersonate') }}" class="btn btn-sm btn-light ms-3 text-danger fw-bold">Stop Impersonating</a>
+        <a href="{{ url_for('admin.stop_impersonate') }}" class="btn btn-sm btn-light ms-3 text-danger fw-bold">Stop Impersonating</a>
     </div>
     {% endif %}
     <nav class="navbar navbar-expand-lg navbar-dark bg-dark mb-4">