feat: configurable Content Safety violation messages

[paullizer]

Summary

• Add an Admin Settings Markdown editor for the Content Safety violation message, using the existing local SimpleMDE toolbar.
• Persist a configurable message and an Include Trigger Information switch; the switch controls whether reasons, categories/severities, and blocklist matches are appended.
• Consolidate normal and streaming Content Safety response formatting in a shared helper, preserving the previous detailed default behavior.
• Stabilize the hidden Safety-tab editor: it refreshes after visible layout settles, Markdown-only edits enable Save Settings, and the editor synchronizes into the submitted form field.
• Add seeded defaults, regression coverage, feature documentation, release notes, and the 0.250.061 application version bump.

Design Note

The implementation uses an explicit trigger-information toggle rather than template placeholders. This gives administrators the requested choice to include or omit violation details without interpolating dynamic values into the Markdown template.

Validation

• python -m pytest -q functional_tests/test_content_safety_violation_message.py - 5 passed
• python scripts/check_swagger_routes.py application/single_app/route_backend_chats.py application/single_app/route_frontend_admin_settings.py - passed
• Route policy suites - 12 passed
• python scripts/check_xss_sinks.py --base-sha origin/Development --head-sha HEAD ... - passed
• python scripts/check_broken_access_control.py --base-sha origin/Development --head-sha HEAD ... - passed
• Python compilation, JavaScript editor-script syntax, and full branch whitespace checks - passed
• Live browser validation as an administrator:
  • Safety Violation Message shows the standard 12-control Markdown toolbar.
  • Markdown-only edits activate Save Settings and persist after a full reload.
  • A policy-blocked chat rendered the configured Markdown message, omitted trigger details when disabled, and retained the Safety Violations link.
  • The original local Admin Settings value was restored after the test.

Fixes #989