Finalize the Python portfolio presentation

[DataTideHH]

Summary

Finalizes python-data-basics as a recruiter- and reviewer-oriented portfolio repository without adding artificial technical scope.

README changes

• replaces the long chronological learning narrative with a concise end-to-end Data/BI story
• leads with the tested business-relevant workflow rather than environment setup
• adds a five-minute technical review path
• surfaces verified control totals and reconciliation behaviour
• keeps the Matplotlib evidence charts visible
• clarifies notebook hygiene, CI coverage, data safety and scope boundaries
• links the repository more clearly to the wider DataTideHH portfolio

Project status

Adds docs/project-status.md and marks the repository as portfolio-complete / maintenance mode.

Future changes are intentionally limited mainly to compatibility, defects, documentation and safety improvements. Unrelated exercises, artificial scale, dashboard layers and cloud deployment remain out of scope for this repository.

Validation

The documentation change triggers the existing complete Python 3.12 matrix through the new docs/project-status.md file. The PR will be merged only after Ubuntu 24.04 and Windows 2025 both complete successfully.

Follow-up outside this PR

After merge, the GitHub profile repository will be updated to describe the completed data-quality, KPI-reconciliation, reporting and cross-platform CI evidence. Repository About text and Topics will also be aligned with the final scope.