feat: Enhance playlist management and GUI logic

- Improved playlist item fetching by adding robust pagination and low-level request hooks for better testing and flexibility.
- Refactored track ID extraction logic into reusable helpers for clarity.
- Improved initialization for dialog components to avoid circular dependencies in the GUI.
- Added new unit tests to validate playlist operations, including track addition/removal and API integration.
- Updated metadata functions to simplify dictionary access using `.get` for better readability.
- Ensured PySide6 system dependencies are installed in GitHub Actions to address CI compatibility issues.
- Streamlined UI package initialization to improve modularity and robustness of imports.

.github/workflows/master.yml

@@ -43,6 +43,21 @@ jobs:
       - name: Install Poetry
         uses: snok/install-poetry@v1
 
+      - name: Install system dependencies for PySide6
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y \
+            libegl1 \
+            libgl1 \
+            libxkbcommon-x11-0 \
+            libxcb-xinerama0 \
+            libxrandr2 \
+            libxrender1 \
+            libxi6 \
+            libxcomposite1 \
+            libxdamage1 \
+            libxtst6
+
       - name: Load cached venv
         uses: actions/cache@v4
         with:
@@ -55,6 +70,8 @@ jobs:
           python -m pip install tox tox-gh-actions
 
       - name: Test with tox
+        env:
+          QT_QPA_PLATFORM: offscreen
         run: tox
 
   check-docs: