Add /sync_x command with X bookmarks import flow

vendor/extract-x-bookmarks/README.md

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+# extract-x-bookmarks
+Written by ChatGPT, not me.
+
+[Works fine](https://x.com/thegeneralist01/status/2003819489989926932).
+
+## Requirements
+- Python
+- Dependencies in `requirements.txt`
+
+## Usage
+- Create a virtual environment if you want (`uv venv .venv` or whatever), then activate it. (This is absolutely optional).
+
+- Install dependencies:
+```bash
+pip install -r requirements.txt
+```
+
+- Now, to get the **Cloudflare cookies,** this is quickest way I use:
+    - Download the [Cookie-Editor extension](https://cookie-editor.com/).
+    - Open your browser and go to [Twitter](https://x.com).
+    - Open the Cookie-Editor extension, press the export button (bottom right) and export as Header String. (It will copy it to the clipboard).
+    - Open the terminal, and run (the python file):
+    ```bash
+    python isolate_cookies.py
+    ```
+    - Paste the clipboard content.
+    - It will then put the two needed cookies into `creds.txt`, which the script will use.
+        - **If you want to do that without installing the extension,** the `creds.txt` file will have the following format:
+        ```
+        auth_token=blablabla;ct0=blablabla
+        ```
+
+- A few things to know before running the script:
+    - It will create a `bookmarks.txt` file with the URLs of your bookmarks.
+    - The script fetches about 90 bookmarks per run. That means you might want to continually run it until you have no cookies left.
+        - A run writes (appends, really) URLs in a descending order (newest first).
+    - It might ask you whether to prepend or append the URLs - whether a new run should add URLs to the start or end of the file. **Generally, for a linear timeline, you want to append,** so: `a`.
+    - It will take some time in the end to **unbookmark** the fetched bookmarks. Each time 10 new bookmarks are unbookmarked, it will print a message.
+
+- Run the script until you have all your bookmarks extracted:
+```bash
+python main.py
+```
+
+## License
+Licensed under the [MIT License](LICENSE).