feat(app): scaffold Vue3 frontend (stage 1)

app.py

@@ -1241,6 +1241,37 @@ def admin_page():
     except Exception as e:
         logger.error(f"[admin_spa] 加载manifest失败: {e}")
         return render_template('admin_legacy.html')
+
+
+def render_app_spa_or_legacy(legacy_template_name: str):
+    """渲染前台 Vue SPA（构建产物位于 static/app），失败则回退旧模板。
+
+    说明：该函数仅负责“资源注入/回退逻辑”，不改变任何接口与业务流程。
+    """
+    manifest_path = os.path.join(app.root_path, 'static', 'app', '.vite', 'manifest.json')
+    try:
+        with open(manifest_path, 'r', encoding='utf-8') as f:
+            manifest = json.load(f)
+
+        entry = manifest.get('index.html') or {}
+        js_file = entry.get('file')
+        css_files = entry.get('css') or []
+
+        if not js_file:
+            logger.warning(f"[app_spa] manifest缺少入口文件: {manifest_path}")
+            return render_template(legacy_template_name)
+
+        return render_template(
+            'app.html',
+            app_spa_js_file=f'app/{js_file}',
+            app_spa_css_files=[f'app/{p}' for p in css_files],
+        )
+    except FileNotFoundError:
+        logger.info(f"[app_spa] 未找到manifest: {manifest_path}，回退旧模板: {legacy_template_name}")
+        return render_template(legacy_template_name)
+    except Exception as e:
+        logger.error(f"[app_spa] 加载manifest失败: {e}")
+        return render_template(legacy_template_name)
 # ==================== 用户认证API ====================
 
 @app.route('/api/register', methods=['POST'])