fix: eliminate async safety violations and migrate to pathlib (#697)

## ℹ️ Description
Eliminate all blocking I/O operations in async contexts and modernize
file path handling by migrating from os.path to pathlib.Path.

- Link to the related issue(s): #692 
- Get rid of the TODO in pyproject.toml
- The added debug logging will ease the troubleshooting for path related
issues.

## 📋 Changes Summary

- Enable ASYNC210, ASYNC230, ASYNC240, ASYNC250 Ruff rules
- Wrap blocking urllib.request.urlopen() in run_in_executor
- Wrap blocking file operations (open, write) in run_in_executor
- Replace blocking os.path calls with async helpers using
run_in_executor
- Replace blocking input() with await ainput()
- Migrate extract.py from os.path to pathlib.Path
- Use Path() constructor and / operator for path joining
- Use Path.mkdir(), Path.rename() in executor instead of os functions
- Create mockable _path_exists() and _path_is_dir() helpers
- Add debug logging for all file system operations

### ⚙️ Type of Change
Select the type(s) of change(s) included in this pull request:
- [X] 🐞 Bug fix (non-breaking change which fixes an issue)
- [ ] ✨ New feature (adds new functionality without breaking existing
usage)
- [ ] 💥 Breaking change (changes that might break existing user setups,
scripts, or configurations)


## ✅ Checklist
Before requesting a review, confirm the following:
- [X] I have reviewed my changes to ensure they meet the project's
standards.
- [X] I have tested my changes and ensured that all tests pass (`pdm run
test`).
- [X] I have formatted the code (`pdm run format`).
- [X] I have verified that linting passes (`pdm run lint`).
- [X] I have updated documentation where necessary.

By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice.


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Refactor**
  * Made user prompt non‑blocking to improve responsiveness.
* Converted filesystem/path handling and prefs I/O to async‑friendly
operations; moved blocking network and file work to background tasks.
* Added async file/path helpers and async port‑check before browser
connections.

* **Tests**
* Expanded unit tests for path helpers, image download success/failure,
prefs writing, and directory creation/renaming workflows.

<sub>✏️ Tip: You can customize this high-level summary in your review
settings.</sub>
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

src/kleinanzeigen_bot/utils/files.py

@@ -1,7 +1,8 @@
 # SPDX-FileCopyrightText: © Sebastian Thomschke and contributors
 # SPDX-License-Identifier: AGPL-3.0-or-later
 # SPDX-ArtifactOfProjectHomePage: https://github.com/Second-Hand-Friends/kleinanzeigen-bot/
-import os
+import asyncio, os  # isort: skip
+from pathlib import Path
 
 
 def abspath(relative_path:str, relative_to:str | None = None) -> str:
@@ -24,3 +25,23 @@ def abspath(relative_path:str, relative_to:str | None = None) -> str:
         base = os.path.dirname(base)
 
     return os.path.normpath(os.path.join(base, relative_path))
+
+
+async def exists(path:str | Path) -> bool:
+    """
+    Asynchronously check if a file or directory exists.
+
+    :param path: Path to check
+    :return: True if path exists, False otherwise
+    """
+    return await asyncio.get_running_loop().run_in_executor(None, Path(path).exists)
+
+
+async def is_dir(path:str | Path) -> bool:
+    """
+    Asynchronously check if a path is a directory.
+
+    :param path: Path to check
+    :return: True if path is a directory, False otherwise
+    """
+    return await asyncio.get_running_loop().run_in_executor(None, Path(path).is_dir)