Wrap all linting commands in tox

Currently, linting in CKI projects is implemented inconsistently across CI/CD workflows. Some linting steps are hardcoded directly into CI/CD templates, while others are executed via tox through the cki_lint.sh script.

This fragmented approach results in:

• Low maintainability of linting logic and scripts.
• Poor traceability, with multiple, undocumented entry points to run linters.
• A confusing developer experience, as reproducing CI linting behavior locally often requires trial and error or deep knowledge of internal scripts.

To improve maintainability and developer usability, this issue aims to:

• Consolidate linting execution into a single, consistent path (preferably via tox or shared reusable CI steps).
• Ensure developers can easily run the exact same linting checks locally as in CI, with minimal setup and clear instructions.