Make function_call_timeout_secs optional and skip timeout task when unset

Change the default from 10s to None so deferred function calls can run
indefinitely when no timeout is configured. Only create the timeout
task when a timeout is actually provided (per-call or service-level).

src/pipecat/services/llm_service.py

@@ -185,7 +185,7 @@ class LLMService(UserTurnCompletionLLMServiceMixin, AIService):
     def __init__(
         self,
         run_in_parallel: bool = True,
-        function_call_timeout_secs: float = 10.0,
+        function_call_timeout_secs: Optional[float] = None,
         settings: Optional[LLMSettings] = None,
         **kwargs,
     ):
@@ -194,8 +194,8 @@ class LLMService(UserTurnCompletionLLMServiceMixin, AIService):
         Args:
             run_in_parallel: Whether to run function calls in parallel or sequentially.
                 Defaults to True.
-            function_call_timeout_secs: Timeout in seconds for deferred function calls.
-                Defaults to 10.0 seconds.
+            function_call_timeout_secs: Optional timeout in seconds for deferred function
+                calls.
             settings: The runtime-updatable settings for the LLM service.
             **kwargs: Additional arguments passed to the parent AIService.
 
@@ -753,11 +753,7 @@ class LLMService(UserTurnCompletionLLMServiceMixin, AIService):
         # Start a timeout task for deferred function calls
         async def timeout_handler():
             try:
-                effective_timeout = (
-                    item.timeout_secs
-                    if item.timeout_secs is not None
-                    else self._function_call_timeout_secs
-                )
+                effective_timeout = item.timeout_secs or self._function_call_timeout_secs
                 await asyncio.sleep(effective_timeout)
                 logger.warning(
                     f"{self} Function call [{runner_item.function_name}:{runner_item.tool_call_id}] timed out after {effective_timeout} seconds."
@@ -768,13 +764,15 @@ class LLMService(UserTurnCompletionLLMServiceMixin, AIService):
             except asyncio.CancelledError:
                 raise
 
-        timeout_task = self.create_task(timeout_handler())
+        if item.timeout_secs or self._function_call_timeout_secs:
+            timeout_task = self.create_task(timeout_handler())
+
+        # Yield to the event loop so the timeout task coroutine gets entered
+        # before it could be cancelled. Without this, cancelling the task before
+        # it starts would leave the coroutine in a "never awaited" state.
+        await asyncio.sleep(0)
 
         try:
-            # Yield to the event loop so the timeout task coroutine gets entered
-            # before it could be cancelled. Without this, cancelling the task before
-            # it starts would leave the coroutine in a "never awaited" state.
-            await asyncio.sleep(0)
             if isinstance(item.handler, DirectFunctionWrapper):
                 # Handler is a DirectFunctionWrapper
                 await item.handler.invoke(