Add Dify integration and enhance workflow node specifications

- Introduce new fields `dify_api_url` and `dify_api_key` in `AssistantConfig` for Dify API integration.
- Update `requirements.txt` to include `dify-client-python` for Dify SDK support.
- Modify `config_resolver` to handle Dify connection information.
- Add a new `globalNode` type in workflow specifications to provide unified settings across workflows.
- Enhance node specifications with additional constraints and default values for better configuration management.
- Update frontend components to support the new `globalNode` type and its properties, improving workflow editor functionality.

backend/services/pipecat/call_lifecycle.py

@@ -0,0 +1,60 @@
+"""Shared call termination timing for prompt tools and workflow end nodes."""
+
+from __future__ import annotations
+
+from collections.abc import Awaitable, Callable
+
+from loguru import logger
+from pipecat.frames.frames import BotStartedSpeakingFrame, BotStoppedSpeakingFrame
+from pipecat.processors.frame_processor import FrameDirection, FrameProcessor
+
+
+class CallEndCoordinator:
+    """End immediately or after the currently armed closing speech finishes."""
+
+    def __init__(self, queue_end: Callable[[str], Awaitable[None]]):
+        self._queue_end = queue_end
+        self._ending = False
+        self._armed = False
+        self._speaking = False
+        self._finished = False
+        self._reason = "completed"
+
+    @property
+    def ending(self) -> bool:
+        return self._ending
+
+    def begin(self, reason: str) -> None:
+        self._ending = True
+        self._reason = reason or "completed"
+
+    def arm_after_speech(self) -> None:
+        self._armed = True
+
+    async def finish(self) -> None:
+        if self._finished:
+            return
+        self._finished = True
+        await self._queue_end(self._reason)
+
+    async def observe(self, frame) -> None:
+        if isinstance(frame, BotStartedSpeakingFrame) and self._armed:
+            self._speaking = True
+        elif (
+            isinstance(frame, BotStoppedSpeakingFrame)
+            and self._armed
+            and self._speaking
+        ):
+            logger.info("结束语播报完毕,挂断通话")
+            await self.finish()
+
+
+class EndCallAfterSpeechProcessor(FrameProcessor):
+    def __init__(self, coordinator: CallEndCoordinator):
+        super().__init__()
+        self._coordinator = coordinator
+
+    async def process_frame(self, frame, direction: FrameDirection):
+        await super().process_frame(frame, direction)
+        await self.push_frame(frame, direction)
+        await self._coordinator.observe(frame)