Redesign PDF template, add batch letter generator, extend tests and seed data

[liocle]

🧾 Summary

This PR introduces a redesigned welcome letter template with structured typography and layout, and adds tooling to batch-generate PDFs. It also expands seed data, improves test coverage, and mounts new template volumes into Docker for live development.

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✅ What’s Included

📄 Letter Template (HTML/CSS)

• Complete rewrite of welcome_letter.html.jinja2:
  • Declarative layout using CSS custom properties
  • Absolute-positioned sender/recipient blocks
  • Sectioned title, body, and payment info
  • Link and email styling
• Placeholder content to be localized/updated later

🛠 Makefile Utility

• Added make generate_letters:

  generate_letters:
  	docker compose exec api python scripts/generate_letters.py

• Can be chained after make create_db && make seed_db

🧪 Testing

• Added new route test files:
  • test_routes_member_search.py — full coverage of all search endpoints
  • test_routes_membership.py — tests /members/{id}/memberships
  • test_routes_misc.py — validates /misc/* endpoints
• Patched conftest.py to ensure example.test → example.com for better email consistency

🌱 Seed Data Enhancements

• Added:
  • Diana — new unpaid member (2025)
  • Erkki — historical + unpaid membership

🐳 Docker Development Volumes

• Mounted:
  • app/pdf/templates/ for live letter previewing
  • Ensures you can tweak layout without rebuilding the image

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🧪 How to Test

make create_db
make seed_db
make generate_letters

• PDFs saved to output/letters/
• API check:

  curl -X POST http://localhost:8000/members/1/generate_welcome_letter

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🧭 Follow-up Ideas

• Generate PDFs at time of /new_member creation
• Automatically email PDF to member