feat: add automated testing framework with initial unit test suite for core modules

- Introduces pytest-based test infrastructure covering data validation, API endpoints, and utility functions
- Configures CI pipeline to run tests on every push to main branch
- Adds test fixtures and mock objects for isolated component testing

.gitea/workflows/test.yml

@@ -12,6 +12,10 @@ jobs:
       PIP_BREAK_SYSTEM_PACKAGES: 1
     runs-on: ubuntu-latest
     steps:
+    - name: Create virtual environment
+      run: |
+        python -m venv venv
+        . venv/bin/activate
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip