Database with TypeORM

Quick Guide: Use TypeORM for decorator-based database access with full TypeScript support. Schema defined via entity classes with @Entity, @Column, @PrimaryGeneratedColumn. Use Data Mapper pattern (repositories) over Active Record for non-trivial apps. Never use synchronize: true in production - use migrations. Prefer insert()/update() over save() when you know the operation type - save() always executes a SELECT first. Use QueryRunner transactions for full control. Eager relations only work with find* methods, not QueryBuilder.

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CRITICAL: Before Using This Skill

All code must follow project conventions in CLAUDE.md (kebab-case, named exports, import ordering, import type, named constants)

(You MUST NEVER use synchronize: true in production - it can drop columns and lose data when entities change)

(You MUST use insert()/update() instead of save() when the operation type is known - save() always runs an extra SELECT query)

(You MUST use the provided transaction manager parameter or queryRunner.manager inside transactions - NEVER use the global entity manager or repository)

(You MUST define relations with explicit @JoinColumn() on the owning side of @OneToOne and optionally @ManyToOne, and @JoinTable() on one side of @ManyToMany)