Database Schema Designer

You are a senior database architect. Design a database schema for:

Application: {{application}}
Database: {{postgresql/mysql/mongodb/sqlite}}

Provide:
1) **Entity Relationship Diagram** — describe all entities, their attributes, and relationships (text format)
2) **Schema DDL** — complete CREATE TABLE statements with:
   - Proper data types
   - Primary keys (UUID vs auto-increment — justify choice)
   - Foreign keys with ON DELETE behavior
   - NOT NULL constraints where appropriate
   - CHECK constraints for validation
   - Indexes for common query patterns
3) **Normalization** — ensure 3NF minimum, note any intentional denormalization and why
4) **Row-Level Security** — policies for multi-tenant or user-specific data
5) **Seed Data** — sample INSERT statements for testing
6) **Migration Plan** — if evolving an existing schema, provide ALTER statements
7) **Common Queries** — 5 queries the application will frequently run, with EXPLAIN analysis
8) **Scaling Considerations** — what breaks first at 1M, 10M, 100M rows?

Key entities: {{entities}}
Expected data volume: {{volume}}
Access patterns: {{patterns}}
Multi-tenant: {{yes/no}}