feat(feed): add template card sections

[SebastianBoehler]

Summary

• rework the For you feed into typed template sections for today's schedule, Tübingen highlights, and emails
• add clickable schedule/article/email card layouts with popup detail sheets and AI/send/navigation actions
• keep structured local-LLM fields in the feed models so future parsers or on-device LLM output can fill the UI without another layout rewrite

Validation

• git diff --check
• local Flutter/Dart checks could not run because this runtime does not have flutter or dart installed; GitHub Actions should be used for formatting/analyze/tests