feat: update codebase to use httpx2 and enhance docstrings for clarity

app/services/scheduler.py

@@ -1,3 +1,5 @@
+"""Background database health-check scheduling."""
+
 from collections.abc import AsyncIterator
 from contextlib import asynccontextmanager
 from datetime import datetime
@@ -15,7 +17,8 @@ from app.database import AsyncSessionFactory, engine
 logger = get_logger()
 
 
-async def tick():
+async def tick() -> bool:
+    """Run the scheduler's lightweight database heartbeat."""
     async with AsyncSessionFactory() as session:
         stmt = text("select 1;")
         await logger.ainfo(f">>>> Be or not to be...{datetime.now()}")
@@ -26,6 +29,7 @@ async def tick():
 
 @asynccontextmanager
 async def scheduler_lifespan() -> AsyncIterator[None]:
+    """Start the scheduler and stop it when the app lifespan ends."""
     scheduler = AsyncScheduler(
         SQLAlchemyDataStore(engine, schema="scheduler"),
         RedisEventBroker(client_or_url=global_settings.redis_url.unicode_string()),