Add operator forum creation flows

[shaypal5]

Summary

• add a working operator Create Forum form on the Forums dashboard
• add structured forum_creation suggestions with first-class forum fields and an operator Approve & Create action
• add migration support, CLI suggest-forum, API schema/docs, and validation tests

Verification

• npm run check
• npm run test
• npm run build
• Playwright smoke: opened the Forums tab, clicked Create Forum, verified form fields, slug derivation, disabled/enabled submit state

Deployment notes

• apply migrations/postgres/0006_forum_creation_suggestions.sql before deploying the Adanim build