Add v4.4 bridge release runway

[sidmohan0]

Summary

This PR prepares the v4.4 bridge release before v5.0 and adds contributor workflow scaffolding for the open source project.

It includes:

• Python 3.13 core/CLI metadata and CI/release validation.
• v5-preview top-level APIs: datafog.scan, datafog.redact, and datafog.protect.
• Targeted migration warnings for datafog.detect and datafog.process with no import-time warnings.
• Pydantic v2 warning cleanup in DataFog-owned models/config.
• v4.4 bridge docs plus v5 product brief, compatibility matrix, and release cut line.
• Contributor docs, PR template, issue templates, and security policy.

Type

• Bug fix
• Feature
• Docs
• Tests
• Chore

Target Branch

• This PR targets dev
• This PR targets main for a release/hotfix

Validation

Commands run:

.venv313/bin/python -m pytest tests/ -m "not slow" \
  --ignore=tests/test_gliner_annotator.py \
  --ignore=tests/test_image_service.py \
  --ignore=tests/test_ocr_integration.py \
  --ignore=tests/test_spark_integration.py \
  --ignore=tests/test_text_service_integration.py

.venv313/bin/sphinx-build -b html docs docs/_build/html
ruby -e 'require "yaml"; Dir[".github/**/*.yml", ".github/**/*.yaml"].each { |f| YAML.load_file(f); puts "ok #{f}" }'
git diff --check

Results:

• Python 3.13 core/CLI suite: 482 passed, 10 skipped, 291 deselected, 19 xfailed.
• Sphinx docs build passed.
• Workflow and issue-template YAML parsed.
• Diff whitespace check passed.

Optional profiles tested:

• core
• cli
• nlp
• nlp-advanced
• ocr
• distributed

Notes For Reviewers

The top-level preview APIs default to the lightweight regex engine so the core install stays quiet without optional NLP extras. Users can still opt into engine="smart" explicitly.

After this lands, branch rules should be updated to require PRs into dev, disable force pushes on dev, require at least one approval, require conversation resolution, and align required status-check names with the actual CI matrix jobs.