feat: add Spotify client and auth routes

backend/app/main.py

@@ -1,23 +1,53 @@
 """Application factory and wiring. No logic lives here."""
 
+from collections.abc import AsyncIterator
+from contextlib import asynccontextmanager
 from pathlib import Path
 
+import httpx2
 from fastapi import FastAPI
 from fastapi.staticfiles import StaticFiles
 
-from app.config import settings
+from app.adapters.spotify.session import PendingLogins, SessionStore
+from app.api.routes import router
+from app.config import AppMode, Settings, settings
 
 FRONTEND_DIST = Path(__file__).parent / "static"
 
 
-def create_app() -> FastAPI:
+def create_app(
+    application_settings: Settings | None = None,
+    http_transport: httpx2.AsyncBaseTransport | None = None,
+) -> FastAPI:
     """Build the FastAPI app: API routes plus the built SPA on one port."""
-    app = FastAPI(title="discovery-by-llm", docs_url=None, redoc_url=None)
+    active_settings = application_settings or settings
+
+    @asynccontextmanager
+    async def lifespan(application: FastAPI) -> AsyncIterator[None]:
+        if active_settings.app_mode is AppMode.LIVE and not active_settings.spotify_client_id:
+            raise RuntimeError("SPOTIFY_CLIENT_ID is required in live mode")
+        async with httpx2.AsyncClient(
+            timeout=active_settings.spotify_timeout_seconds,
+            transport=http_transport,
+        ) as http:
+            application.state.http = http
+            application.state.session_store = SessionStore()
+            application.state.pending_logins = PendingLogins()
+            application.state.settings = active_settings
+            yield
+
+    app = FastAPI(
+        title="discovery-by-llm",
+        docs_url=None,
+        redoc_url=None,
+        lifespan=lifespan,
+    )
 
     @app.get("/api/health")
     def health() -> dict[str, str]:
-        return {"status": "ok", "mode": settings.app_mode}
+        return {"status": "ok", "mode": active_settings.app_mode}
 
+    app.include_router(router)
     if FRONTEND_DIST.is_dir():
         app.mount("/", StaticFiles(directory=FRONTEND_DIST, html=True), name="spa")