Harden type/data model consistency for chatrooms and realtime events

[ocrichardbot]

Summary

This PR tackles the type-consistency hardening gap by aligning DB schema types and event payload contracts across API + realtime layers.

Changes

• Convert chatrooms.is_private from text ("0"/"1") to boolean in Drizzle schema
• Convert chatroom_invites.max_uses from text to integer in Drizzle schema
• Add migration 0001_type_hardening.sql to safely convert existing values
• Add zod request validation for POST /api/chatrooms
• Update chatroom creation to persist boolean isPrivate directly
• Update invite usage-limit check to use integer maxUses directly
• Fix realtime frontend types to use UUID strings for updatedBy.id and member.id

Why

• Removes fragile text-to-boolean and text-to-number coercions
• Reduces runtime mismatch risk between backend UUIDs and frontend event types
• Adds API boundary validation for more predictable behavior

Notes

• I could not run project lint/tests in this environment because bun is not installed on the host (bun: command not found).