Fix duplicate SEO route registration

Remove sitemap.xml and robots.txt route registrations from app.py
since they're already defined in routes.py. This was causing an
AssertionError on startup.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/smarttools/web/app.py

@@ -12,7 +12,6 @@ from smarttools.registry import app as registry_app
 from . import web_bp
 from .auth import login, register, logout
 from .filters import register_filters
-from .seo import sitemap_response, robots_txt
 from .sessions import SQLiteSessionInterface, cleanup_expired_sessions
 
 
@@ -46,10 +45,6 @@ def create_web_app() -> Flask:
 
     cleanup_expired_sessions()
 
-    # SEO routes
-    app.add_url_rule("/sitemap.xml", endpoint="web.sitemap", view_func=sitemap_response)
-    app.add_url_rule("/robots.txt", endpoint="web.robots", view_func=robots_txt)
-
     # Error handlers
     @app.errorhandler(404)
     def not_found_error(error):