Docs: rewrite README with clear Docker and Docker Compose instructions; refactor app into package (auth, admin, pages, db); keep single entrypoint app.py

app/auth.py

@@ -0,0 +1,41 @@
+from flask import Blueprint, current_app, render_template, request, redirect, url_for, session, abort, flash
+
+
+auth_bp = Blueprint("auth", __name__)
+
+
+def is_logged_in() -> bool:
+    return bool(session.get("logged_in"))
+
+
+def login_required():
+    if not is_logged_in():
+        abort(404)
+
+
+@auth_bp.app_context_processor
+def inject_auth():
+    return {"logged_in": is_logged_in()}
+
+
+@auth_bp.route("/login", methods=["GET", "POST"])
+def login():
+    if request.method == "POST":
+        username = request.form.get("username", "")
+        password = request.form.get("password", "")
+        if (
+            username == current_app.config["ADMIN_USERNAME"]
+            and password == current_app.config["ADMIN_PASSWORD"]
+        ):
+            session["logged_in"] = True
+            flash("Вход выполнен", "success")
+            return redirect(url_for("admin.index"))
+        flash("Неверные логин или пароль", "error")
+    return render_template("login.html")
+
+
+@auth_bp.route("/logout", methods=["POST"])
+def logout():
+    session.clear()
+    abort(404)
+