Add AI chat with skills management and model provider settings

- Model providers for OpenAI and Anthropic message formats (e.g. via
  Sub2API), with API keys encrypted at rest and never returned
- Skills tree with markdown editing, priorities, drafts, publishing and
  rollback; only published skills enter the chat prompt
- Chat page with tool calls over collected news and Binance USD-M
  klines, a persisted CONTEXT.md, reset, and stop-generation support
- Chat may only create skill drafts and update CONTEXT.md; publishing,
  deleting, moving and priority changes stay with the user

backend/src/alphapulse/api/main.py

@@ -2,7 +2,7 @@ from fastapi import Depends, FastAPI
 from fastapi.openapi.docs import get_swagger_ui_html
 from fastapi.responses import HTMLResponse
 
-from alphapulse.api import auth, crawler, market, news
+from alphapulse.api import auth, chat, crawler, market, news, settings, skills
 from alphapulse.core.auth import require_admin
 
 # 关闭默认文档路由，改为登录后才能访问
@@ -12,6 +12,9 @@ app.include_router(news.router)
 app.include_router(crawler.router)
 app.include_router(market.router)
 app.include_router(market.ws_router)
+app.include_router(settings.router)
+app.include_router(skills.router)
+app.include_router(chat.router)
 
 
 @app.get("/api/health", include_in_schema=False)