ci: add release workflows

[giscebot]

Summary

• Add the version bump workflow based on merged PR labels, adapted from gisce/codigospostales.
• Add the tag-based GitHub Release and PyPI publish workflow, also based on gisce/codigospostales.
• Add .bumpversion.cfg initialized with the current cini version, 0.7.4.

Validation

• Parsed both workflow YAML files with python3/PyYAML.
• Checked that setup.py version matches .bumpversion.cfg.
• Ran git diff --check.

Operational notes

• The workflow expects the same Actions secrets as the reference repo: PUB_MASTER_PUSH_TOKEN, RO_GH_ACTIONS_TOKEN and PYPI_MASTER_TOKEN.
• Release labels major/minor/patch are available in the repo; patch was added to match the bump workflow.

[giscebot]

Post-merge verification done.

• PR ci: add release workflows #48 was merged as fb17ab5 and is contained in origin/master.
• The new bump workflow ran after the merge and created b025802 (Bump to v0.7.5).
• setup.py and .bumpversion.cfg now both report 0.7.5 on origin/master.
• Final workflow YAML files parse correctly with PyYAML.
• Post-merge Actions are green: BUMP Version, Python 2.7, Python 3.11, and Upload package to PYPI all completed successfully.
• GitHub release is published: https://github.com/gisce/cini/releases/tag/v0.7.5

No follow-up code change needed from my side.