docs: add documentation for predefined questions to load on startup (#22)

Author: toddeTV

docs/predefined-questions.md

@@ -0,0 +1,39 @@
+# Predefined Questions
+
+This document explains how to automatically load a set of questions into the application when it starts up. This is useful for populating the quiz with initial data without manual entry.
+
+## How It Works
+
+1.  **Create the File**: In the `data/` directory, create a file named `predefined-questions.json`.
+
+2.  **File Format**: The file must contain a JSON array of question objects. Each object must have a `question_text` (string) and `answer_options` (an array of objects, each with a `text` property).
+
+    **Example `data/predefined-questions.json`:**
+    ```json
+    [
+      {
+        "question_text": "What is your favorite color?",
+        "answer_options": [
+          { "text": "Red" },
+          { "text": "Green", "emoji": "💚" },
+          { "text": "Blue" }
+        ]
+      },
+      {
+        "question_text": "Which technology do you prefer?",
+        "answer_options": [
+          { "text": "Frontend" },
+          { "text": "Backend" }
+        ]
+      }
+    ]
+    ```
+
+3.  **Processing**:
+    - When the application starts, it checks for the existence of `data/predefined-questions.json`.
+    - If found, it renames the file to `data/predefined-questions.json.processing` to prevent it from being processed again.
+    - It reads the questions from the `.processing` file and adds any questions that do not already exist (based on `question_text`) to the main `data/questions.json` file.
+    - After successful processing, the `.processing` file is deleted.
+    - If an error occurs (e.g., malformed JSON), the `.processing` file is left in place for manual inspection.
+
+This ensures that predefined questions are loaded exactly once in an atomic and safe manner.