revert: app/ → site/ (drhider proves site/ works fine)

site/routes/pages_bp.py

@@ -0,0 +1,14 @@
+"""HTML-страницы."""
+from flask import Blueprint, render_template
+
+pages_bp = Blueprint("pages", __name__)
+
+
+@pages_bp.route("/")
+def index():
+    return render_template("index.html")
+
+
+@pages_bp.route("/architect")
+def architect():
+    return render_template("architect.html")