refactor: simplify homepage layout, consolidate landing page components

Merge hero/stats/features/footer sections into home-page-content.tsx,
remove separate landing-page.tsx. Update styles, layout, navbar, and
backend config.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/src/core/config.py

@@ -139,7 +139,12 @@ def ensure_directories():
         settings.generated_images_dir,
         os.path.dirname(settings.log_file),
     ]
-    
+
+    # SQLite 数据库目录
+    if not is_postgresql_database():
+        db_path = settings.database_url.replace("sqlite:///", "")
+        directories.append(os.path.dirname(db_path))
+
     for directory in directories:
         Path(directory).mkdir(parents=True, exist_ok=True)