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

deploy/.env.example

@@ -6,3 +6,5 @@ JWT_SECRET=<openssl rand -hex 32>
 ADMIN_USERNAME=admin
 # 哈希含 $，必须用单引号包住，否则 compose 会做变量替换
 ADMIN_PASSWORD_HASH='<python -m alphapulse.core.auth hash-password 的输出>'
+# 加密存库的第三方 API key（Fernet）；丢失后已存的 key 无法解密，需要在页面重新填写
+SECRET_ENCRYPTION_KEY=<python -c "from cryptography.fernet import Fernet; print(Fernet.generate_key().decode())">