Rename BaseTask → BaseWorker and reserve "task" for asyncio

Replaces every "task" identifier that referred to the BaseTask
abstraction with "worker". Asyncio task plumbing (asyncio.Task,
BaseTaskManager, TaskManager, create_task, cancel_task, etc.) stays
untouched. Highlights:

- Classes: BaseTask → BaseWorker, PipelineTask → PipelineWorker,
  LLMTask → LLMWorker, LLMContextTask → LLMContextWorker, TaskBus →
  WorkerBus, TaskRegistry → WorkerRegistry, TaskActivationArgs →
  WorkerActivationArgs, TaskReadyData → WorkerReadyData,
  TaskRegistryEntry → WorkerRegistryEntry, TaskObserver →
  WorkerObserver, all Bus*TaskMessage → Bus*WorkerMessage,
  BusAddTaskMessage.task field → worker, BusWorkerRegistryMessage.tasks
  field → workers.
- Methods/decorators: activate_task → activate_worker, deactivate_task
  → deactivate_worker, add_task → add_worker, watch_task →
  watch_worker, @task_ready → @worker_ready, setup_pipeline_task hook
  → setup_pipeline_worker.
- Params/fields: FrameProcessorSetup.pipeline_task and
  FunctionCallParams.pipeline_task → pipeline_worker. Parameter names
  like task_name → worker_name; spawn/run accept worker:.
- Files: pipeline/base_task.py → base_worker.py, pipeline/task.py →
  worker.py (plus a re-export shim at pipeline/task.py),
  task_observer.py → worker_observer.py, task_ready_decorator.py →
  worker_ready_decorator.py, pipecat.tasks → pipecat.workers,
  llm_task.py → llm_worker.py, llm_context_task.py →
  llm_context_worker.py, examples/multi-task → examples/multi-worker.

Back-compat:
- PipelineTask kept as a deprecated subclass of PipelineWorker that
  warns on construction.
- pipecat.pipeline.task re-exports PipelineWorker/PipelineTask/etc. so
  existing user imports keep working.
- FrameProcessor.pipeline_task kept as a deprecated property that
  forwards to pipeline_worker.

Local variables in examples that hold a worker (task = PipelineTask(...))
are renamed to worker = PipelineWorker(...). Asyncio-task locals
(runner_task, etc.) are preserved.

tests/test_vonage_video_connector.py

@@ -12,6 +12,7 @@ from collections.abc import Awaitable, Callable
 from concurrent.futures import ThreadPoolExecutor
 from dataclasses import dataclass
 from datetime import datetime, timedelta
+from types import SimpleNamespace
 from typing import Any, Optional
 from unittest.mock import ANY, AsyncMock, MagicMock, Mock, call, patch
 
@@ -247,7 +248,11 @@ class TestVonageVideoConnectorTransport:
         clock: SystemClock = SystemClock()  # type: ignore[no-untyped-call]
         task_manager = TaskManager()
         task_manager.setup(TaskManagerParams(loop=asyncio.get_running_loop()))
-        self._frame_processor_setup = FrameProcessorSetup(clock=clock, task_manager=task_manager)
+        self._frame_processor_setup = FrameProcessorSetup(
+            clock=clock,
+            task_manager=task_manager,
+            pipeline_worker=SimpleNamespace(app_resources=None),  # type: ignore[arg-type]
+        )
         return self._frame_processor_setup
 
     async def _wait_for_condition(