Enhance AssistantConfig and pipeline for FastGPT integration

- Add new fields in AssistantConfig for FastGPT connection details, including `fastgpt_api_url`, `fastgpt_api_key`, and `fastgpt_app_id`.
- Update the pipeline to utilize the new FastGPT configuration, ensuring proper integration with external services.
- Introduce type handling for different assistant types, including support for realtime modes and external brain management.
- Refactor frontend components to include hints for FastGPT configuration inputs, improving user guidance during setup.

backend/services/brains/fastgpt_brain.py

@@ -0,0 +1,67 @@
+"""FastGPT 大脑:外部托管,context/KB/tools 全在 FastGPT 服务端。
+
+cascade-only(realtime 不兼容外部大脑)。每通电话持有一个稳定 chatId:
+greeting(get_chat_init)与后续每轮推理共用它,保证服务端上下文连续。
+"""
+
+from __future__ import annotations
+
+from typing import Any
+from uuid import uuid4
+
+from fastgpt_client import AsyncChatClient
+from loguru import logger
+from models import AssistantConfig
+from pipecat.processors.aggregators.llm_context import LLMContext
+from pipecat.processors.frame_processor import FrameProcessor
+
+from services.brains.base import BrainSpec
+from services.brains.fastgpt_llm import FastGPTLLMService, normalize_base_url
+
+
+def _extract_welcome(payload: Any) -> str:
+    """从 get_chat_init 响应里取开场白(welcomeText),多层兜底。"""
+    if not isinstance(payload, dict):
+        return ""
+    data = payload.get("data") if isinstance(payload.get("data"), dict) else payload
+    app = data.get("app") if isinstance(data.get("app"), dict) else {}
+    chat_config = app.get("chatConfig") if isinstance(app.get("chatConfig"), dict) else {}
+    for value in (
+        chat_config.get("welcomeText"),
+        app.get("welcomeText"),
+        data.get("welcomeText"),
+        data.get("opener"),
+        app.get("opener"),
+    ):
+        if isinstance(value, str) and value.strip():
+            return value.strip()
+    return ""
+
+
+class FastGPTBrain:
+    def __init__(self):
+        self.spec = BrainSpec(
+            type="fastgpt",
+            supported_runtime_modes=frozenset({"pipeline"}),
+            owns_context=False,
+        )
+        self._chat_id = uuid4().hex
+
+    async def greeting(self, cfg: AssistantConfig) -> str:
+        """优先用 FastGPT 后台配置的开场白;无 app_id 或取不到时回退 cfg.greeting。"""
+        if not cfg.fastgpt_app_id:
+            return cfg.greeting
+        try:
+            client = AsyncChatClient(
+                api_key=cfg.fastgpt_api_key,
+                base_url=normalize_base_url(cfg.fastgpt_api_url),
+            )
+            response = await client.get_chat_init(cfg.fastgpt_app_id, self._chat_id)
+            welcome = _extract_welcome(response.json())
+            return welcome or cfg.greeting
+        except Exception as exc:  # noqa: BLE001 - 拉取失败不应阻断通话
+            logger.warning(f"FastGPT get_chat_init 失败,回退 cfg.greeting: {exc}")
+            return cfg.greeting
+
+    def build_llm(self, cfg: AssistantConfig, context: LLMContext) -> FrameProcessor:
+        return FastGPTLLMService(cfg, chat_id=self._chat_id)