refactor: deduplicate shared code into shared/ module

Move duplicated files from chat + batch-agent into shared/:
- shared/ws_context.py — Redis-based tool call round-trip
- shared/llm.py — LiteLLM factory (get_llm, embed)
- shared/agents/ — 4 domain agents (task, note, project, timeline)

Update all service imports to use shared.* instead of app.*.
Delete 12 duplicated files across both services.

services/chat/app/deep_agent.py

@@ -16,13 +16,13 @@ from typing import Any, Literal
 from langchain_core.messages import AIMessage, HumanMessage, SystemMessage, ToolMessage
 from langchain_core.tools import tool
 
-from app.agents.note_agent import NOTE_TOOLS
-from app.agents.project_agent import PROJECT_TOOLS
-from app.agents.task_agent import TASK_TOOLS
-from app.agents.timeline_agent import TIMELINE_TOOLS
-from app.llm import get_llm
+from shared.agents.note_agent import NOTE_TOOLS
+from shared.agents.project_agent import PROJECT_TOOLS
+from shared.agents.task_agent import TASK_TOOLS
+from shared.agents.timeline_agent import TIMELINE_TOOLS
+from shared.llm import get_llm
 from app.memory_middleware import MemoryMiddleware
-from app.ws_context import clear_tool_result_collector, execute_on_client, set_tool_result_collector
+from shared.ws_context import clear_tool_result_collector, execute_on_client, set_tool_result_collector
 from app import tracing
 from shared.db import async_session