docs: update README and dev guide

fix: remove displayName + improve avatar upload

fix: user profile route userId field

fix: remove all AI features from frontend

fix: remove AI features + verify user profile schema

fix: ai route logging + community comments endpoint

feat: backend AI proxy route

feat: AI summary for news + AI hint/review for journal

fix: service worker network-first strategy

fix: increase news fetch limit to 100 for more pagination pages

fix: pagination syntax error

feat: news pagination + smaller quick actions on mobile

fix: remove pagination + show all 4 quick actions

fix: show all 4 quick actions on mobile

fix: remove unused toast code from Dashboard