feat: 初始版本，圆角主题与首次管理员引导

app/blueprints/main.py

@@ -0,0 +1,11 @@
+from flask import Blueprint, redirect, url_for, current_app, send_from_directory
+
+bp = Blueprint("main", __name__)
+
+@bp.route("/")
+def index():
+    return redirect(url_for("feed.discover"))
+
+@bp.route("/uploads/<path:filename>")
+def uploads(filename):
+    return send_from_directory(current_app.config["UPLOAD_FOLDER"], filename)