fix(examples): use string type annotation for TYPE_CHECKING import

- Fix NameError in 04_realtime_data.py by quoting RealtimeDataManager type
- Type is imported only for type checking, requires string annotation at runtime

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: TexasCoding

examples/04_realtime_data.py

@@ -38,7 +38,7 @@
     from project_x_py.realtime_data_manager import RealtimeDataManager
 
 
-async def display_current_prices(data_manager: RealtimeDataManager):
+async def display_current_prices(data_manager: "RealtimeDataManager"):
     """Display current prices across all timeframes asynchronously."""
     print("\n📊 Current Prices:")