[ebot] Add Geoportal static pages and feedback form

[ewlarson]

Summary

• update the homepage welcome banner copy for the new Geoportal launch
• add in-portal /about, /help, and /feedback pages, using Karen's draft About/Help copy as the starting point
• add a backend /api/v1/feedback email endpoint with configurable sendmail/SMTP delivery and deployment docs
• update header/footer/error-page links and add focused tests for the new pages and feedback flow

Refs #202, #128, #189, and #205.

Verification

• ruff check app/api/v1/endpoint_modules/feedback.py app/api/v1/endpoint_modules/root.py app/api/v1/endpoints.py app/services/feedback_service.py tests/api/v1/test_feedback_endpoint.py tests/services/test_feedback_service.py
• python -m pytest backend/tests/api/v1/test_feedback_endpoint.py backend/tests/services/test_feedback_service.py
• npm test -- --run app/routes/tests/feedback.test.ts src/tests/pages/AboutPage.test.tsx src/tests/pages/FeedbackPage.test.tsx src/tests/pages/HelpPage.test.tsx src/tests/pages/Home.test.tsx src/tests/pages/page-titles.test.tsx
• targeted npx eslint
• npm run build
• git diff --check
• local browser smoke check for /, /about, /help, and /feedback

Note: the frontend test run logs an existing YouTube DNS warning in the HomePage video test, but the tests pass.