refactor(launch): Replace thread with lifespan event for opening the …

…browser (#421)

Closes #301

src/skore/cli/launch_dashboard.py

@@ -1,11 +1,11 @@
 """Implement the "launch" command."""
 
-import threading
-import time
 import webbrowser
+from contextlib import asynccontextmanager
 from pathlib import Path
 
 import uvicorn
+from fastapi import FastAPI
 
 from skore.cli import logger
 from skore.project import load
@@ -18,11 +18,6 @@ class ProjectNotFound(Exception):
     project_path: Path
 
 
-def __open_browser(port: int):
-    time.sleep(0.5)
-    webbrowser.open(f"http://localhost:{port}")
-
-
 def __launch(project_name: str | Path, port: int, open_browser: bool):
     """Launch the UI to visualize a project.
 
@@ -36,10 +31,14 @@ def __launch(project_name: str | Path, port: int, open_browser: bool):
         Whether to automatically open a browser tab showing the UI.
     """
     project = load(project_name)
-    app = create_app(project=project)
 
-    if open_browser:
-        threading.Thread(target=lambda: __open_browser(port=port)).start()
+    @asynccontextmanager
+    async def lifespan(app: FastAPI):
+        if open_browser:
+            webbrowser.open(f"http://localhost:{port}")
+        yield
+
+    app = create_app(project=project, lifespan=lifespan)
 
     try:
         # TODO: check port is free

src/skore/ui/app.py

@@ -3,15 +3,18 @@
 from fastapi import APIRouter, FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.staticfiles import StaticFiles
+from starlette.types import Lifespan
 
 from skore.project import Project, load
 from skore.ui.dependencies import get_static_path
 from skore.ui.report import router as report_router
 
 
-def create_app(project: Project | None = None) -> FastAPI:
+def create_app(
+    project: Project | None = None, lifespan: Lifespan | None = None
+) -> FastAPI:
     """FastAPI factory used to create the API to interact with `stores`."""
-    app = FastAPI()
+    app = FastAPI(lifespan=lifespan)
 
     # Give the app access to the project
     if not project: