feat(api): external promotion CRUD + audit endpoints

Add 20 API endpoints under /api/external/* covering products, campaigns, keywords, audits, rankings, optimization tasks with org_id filtering.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

platform/backend/app/main.py

@@ -9,7 +9,7 @@ from pathlib import Path
 
 from .database import engine, get_db, init_db
 from .models import Base
-from .api import topics, system, articles, publishing, auth, admin, audit, optimizer_logs, cases, task_logs, task_configs, prompt_configs, llm_configs, system_configs, topic_config, calendar, metrics, assets, tasks, platform_config, collector_mgmt, assistant, config_items, role_configs, menu_configs, search_providers, search_rankings
+from .api import topics, system, articles, publishing, auth, admin, audit, optimizer_logs, cases, task_logs, task_configs, prompt_configs, llm_configs, system_configs, topic_config, calendar, metrics, assets, tasks, platform_config, collector_mgmt, assistant, config_items, role_configs, menu_configs, search_providers, search_rankings, external_promotion
 from .initial_data import import_initial_data
 from .core.scheduler import scheduler
 
@@ -105,6 +105,7 @@ app.include_router(menu_configs.router)
 app.include_router(menu_configs.public_router)
 app.include_router(search_providers.router)
 app.include_router(search_rankings.router)
+app.include_router(external_promotion.router)
 
 # 挂载自动生成的图片（必须先于前端根挂载）
 PROJECT_ROOT_DIR = Path(__file__).parent.parent.parent.parent