Replace TypeORM synchronize: true with a Versioned Migration Workflow Using the TypeORM CLI

[mftee]

Description:
Replace TypeORM synchronize: true (development-only) with an independent, proper migration workflow so schema changes are tracked and reproducible.

Tasks:

• Set synchronize: false in the TypeORM config
• Create src/database/data-source.ts exporting a standalone DataSource for the TypeORM CLI
• Add npm scripts: migration:generate, migration:run, migration:revert
• Generate an initial migration from the existing entities
• Update the setup section of README.md to include migration commands

Acceptance Criteria:

• Running npm run migration:run applies all pending migrations to a fresh database
• Running npm run migration:revert rolls back the last migration
• synchronize: true is no longer used in any environment