perf: consolidate initial navigation loading

backend/main.py

@@ -173,6 +173,31 @@ async def me(user: User = Depends(current_user)):
     return user
 
 
+@app.get("/api/v1/bootstrap")
+async def bootstrap_data(user: User = Depends(current_user), db: AsyncSession = Depends(get_db)):
+    folders = list((await db.scalars(
+        select(Folder)
+        .where(Folder.user_id == user.id, Folder.deleted_at.is_(None))
+        .order_by(Folder.position, Folder.created_at)
+    )).all())
+    lists = list((await db.scalars(
+        select(TaskList)
+        .where(TaskList.user_id == user.id, TaskList.deleted_at.is_(None))
+        .order_by(TaskList.is_inbox.desc(), TaskList.position, TaskList.created_at)
+    )).all())
+    tags = list((await db.scalars(
+        select(Tag).where(Tag.user_id == user.id).order_by(Tag.name, Tag.id)
+    )).all())
+    inbox = next((item for item in lists if item.is_inbox), None)
+    return {
+        "user": UserOut.model_validate(user),
+        "folders": [FolderOut.model_validate(item) for item in folders],
+        "lists": [ListOut.model_validate(item) for item in lists],
+        "tags": [TagOut.model_validate(item) for item in tags],
+        "inbox_id": inbox.id if inbox else None,
+    }
+
+
 @app.post("/api/v1/auth/logout", status_code=204)
 async def logout(
     response: Response,