Waste-audit cleanup: remove debug artifacts, tighten entrypoint/CI, and harden settings

[dendencat]

Motivation

• Remove leftover debug artifacts and duplicated template/static files identified by the waste audit to reduce noise and accidental leaks.
• Prevent unsafe runtime migration generation during container start and detect missing migrations in CI to improve production stability.
• Make tests deterministic in environments without Redis and preserve CSRF behavior while keeping logging robust.
• Consolidate and clarify duplicated/overlapping settings to reduce configuration surprises between environments.

Description

• Removed root-level debug and temporary files (cookies.txt, captured login_response*.html, Playwright debug scripts, test_rest_api.py, static/index.html, malformed template files and templates/static/ duplicates) and added ignore patterns to .gitignore.
• Replaced runtime makemigrations in docker/entrypoint.sh with a dry-run check (makemigrations --check --dry-run) and made application migration apply non-interactively (migrate --noinput).
• Added a pre-test migration check step to the CI workflow (.github/workflows/docker-publish.yml) that runs python manage.py makemigrations --check --dry-run before pytest.
• Hardened techblog_cms/settings.py by creating LOG_DIR, routing file handler to LOG_DIR, consolidating CSRF_TRUSTED_ORIGINS into an env-castable setting, avoiding disabling CSRF middleware for tests, and switching test-time cache to an in-memory LocMemCache/session backend to avoid Redis dependency.
• Made settings_production.py insert SecurityMiddleware only if not already present.
• Improved markdown_filter with a fallback linkifier to ensure plain URLs are linkified even if markdown.extensions.linkify is unavailable.
• Documented repository layout and static-asset policy in README.md to reflect the consolidated structure.

Testing

• Ran python manage.py check which succeeded with no issues.
• Ran TESTING=True python manage.py makemigrations --check --dry-run in CI-style mode which completed successfully.
• Ran the full test suite with python -m pytest -v, resulting in all tests passing (16 passed).
• Attempted docker compose config but it could not be executed in this environment because Docker is not installed (docker: command not found).

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Codex Task