feat(db): add TypeORM migration support for production environments

[hashbk]

Summary

• Replace synchronize: true with a proper migration system for production safety
• Development mode retains synchronize: true for fast iteration; production uses explicit migration files for auditable, controllable schema changes
• Add centralized entity list (src/entities/index.ts) shared by app.module.ts and data-source.ts to prevent entity drift

Changes

File	Change
src/entities/index.ts	New — centralized entity list shared by app.module.ts and data-source.ts
src/data-source.ts	New — TypeORM CLI data source config for migration commands
src/database/migration.service.ts	New — runtime migration execution with existing database detection
src/migrations/1785305180672-InitialSchema.ts	New — initial schema migration with all 26 entities
src/migrations/README.md	New — migration workflow documentation
src/app.module.ts	Modified — conditional synchronize/migrations based on NODE_ENV, use ALL_ENTITIES
src/database/database.module.ts	Modified — add MigrationService provider
src/database/database-init.service.ts	Modified — call migration service before seed data
src/modules/user/entities/invitation.entity.ts	Fix — add explicit type: 'varchar' for nullable note column
package.json	Modified — add migration npm scripts
tsconfig.json	Modified — add ts-node commonjs config for CLI
.env.example	Modified — add NODE_ENV documentation

Behavior Matrix

NODE_ENV	synchronize	migrations	Description
Unset / development	true	skipped	Dev mode: auto-sync schema
production	false	auto-run	Prod mode: explicit migrations

Key Design Decisions

1. MigrationService over migrationsRun: true: TypeORM's migrationsRun executes during DataSource initialization, before any NestJS lifecycle hooks. This prevents marking the initial migration as already run for existing databases, causing "table already exists" errors. MigrationService runs after DI initialization, allowing pre-migration checks.

2. Existing database detection: When upgrading from synchronize: true, the existing database already has all tables. MigrationService detects this and marks the initial migration as already executed, preventing duplicate table creation.

3. Centralized entity list: A shared ALL_ENTITIES array in src/entities/index.ts prevents the common problem of entity lists drifting between app.module.ts and data-source.ts.

Test Plan

• Development mode (no NODE_ENV): synchronize: true works, all tables created
• Production mode with empty database: migrations auto-run, all tables created, seed data initialized
• Production mode with existing database: initial migration marked as already run, no duplicate table creation, existing data preserved
• Migration CLI commands work: npm run migration:generate, npm run migration:show