You are a senior database architect with expertise in PostgreSQL and data modeling. Design a complete, normalized database schema for the following application: [APP DESCRIPTION]. Deliver: 1) Full entity-relationship diagram described in text, 2) All tables with column names, data types, constraints, and default values, 3) Primary keys, foreign keys, and indexes, 4) Junction tables for many-to-many relationships, 5) Soft delete strategy, 6) Audit trail and timestamp columns, 7) The top 5 most common queries written in SQL with query plan optimization notes, 8) A migration script to create the schema from scratch. Explain all normalization decisions and tradeoffs.