Add admin Cosmos DB JSON document query and editor

[Bionic711]

Summary

• Adds an admin-only Cosmos DB JSON document query and editor under Admin Settings > Data Management.
• Supports querying configured Cosmos containers, viewing JSON documents, editing allowed documents, and saving updates through backend validation.
• Adds UI affordances and styling for the JSON editor experience in the Data Management area.
• Adds security-pattern coverage for data management routes and UI coverage for the admin Data Management settings screen.

Fixes #1006

Validation

• git diff --check
• Python compile check for changed Python files
• node --check application/single_app/static/js/admin/admin_data_management.js
• python scripts/check_swagger_routes.py ...
• XSS changed-line check: passed for 6 files
• Broken access control changed-line check: passed for 3 files
• Route policy coverage tests:
  • functional_tests/route_tests/test_route_blueprint_policy_inventory.py
  • functional_tests/route_tests/test_route_unauthenticated_policy_contract.py
  • functional_tests/route_tests/test_route_policy_test_coverage.py
• python functional_tests/test_data_management_security_patterns.py
• python -m pytest -rs ui_tests/test_admin_data_management_settings_ui.py

Test Notes

• ui_tests/test_admin_data_management_settings_ui.py: 1 passed, 1 skipped.
• Skipped test reason: Set SIMPLECHAT_UI_BASE_URL to run this UI test.

Documentation and Release Notes

• Added docs/explanation/features/COSMOS_DB_JSON_EDITOR.md.
• Updated docs/explanation/release_notes.md under version 0.250.051.
• application/single_app/config.py version is 0.250.051.

Security Notes

• No sensitive filename hits for .env, secrets, tokens, sessions, keys, connection strings, or local settings artifacts.
• XSS guardrail passed.
• Broken access control guardrail passed.
• Route decorator and route policy coverage passed.