Improve log upload handling

app/__init__.py

@@ -7,6 +7,15 @@ from app.config import Config
 from app.routes import main_blueprint
 
 
+def _format_size_limit(size_limit_bytes: int) -> str:
+    """Render the upload limit in a friendly unit for error messages."""
+    if size_limit_bytes >= 1024 * 1024:
+        return f"{size_limit_bytes / (1024 * 1024):.0f} MB"
+    if size_limit_bytes >= 1024:
+        return f"{size_limit_bytes / 1024:.0f} KB"
+    return f"{size_limit_bytes} bytes"
+
+
 def create_app(config_class: type[Config] = Config) -> Flask:
     """Application factory used by Flask and Gunicorn."""
     app = Flask(__name__, instance_relative_config=True)
@@ -22,7 +31,11 @@ def create_app(config_class: type[Config] = Config) -> Flask:
 
     @app.errorhandler(RequestEntityTooLarge)
     def handle_file_too_large(_error):
-        flash("The uploaded file is too large.", "danger")
+        size_limit_bytes = int(app.config["MAX_CONTENT_LENGTH"])
+        flash(
+            f"The uploaded file is too large. Maximum allowed size is {_format_size_limit(size_limit_bytes)}.",
+            "danger",
+        )
         return render_template("index.html"), 413
 
     return app