[BE-47] Replace TypeORM `synchronize: true` with proper migrations

[yusuftomilola]

Overview

AppModule sets synchronize: true in the TypeORM config, which automatically alters the database schema on every app start. This can silently drop columns on any non-local environment and is explicitly unsafe for production by the TypeORM docs.

Context

• TypeORM config: backend/src/app.module.ts — synchronize: true on line ~85
• All entity files are in backend/src/*/entities/
• TypeORM CLI uses a separate DataSource config file pointing to entity paths

Tasks

• Set synchronize: false in TypeOrmModule.forRootAsync() config for all environments
• Create backend/src/data-source.ts as the TypeORM CLI data source file:
  • Imports all entity files explicitly
  • Reads DB config from .env via dotenv
  • Points migrations to src/migrations/**/*.ts
• Add the following scripts to backend/package.json:
  • "migration:generate": "ts-node -r tsconfig-paths/register ./node_modules/typeorm/cli migration:generate -d src/data-source.ts"
  • "migration:run": "ts-node -r tsconfig-paths/register ./node_modules/typeorm/cli migration:run -d src/data-source.ts"
  • "migration:revert": "ts-node -r tsconfig-paths/register ./node_modules/typeorm/cli migration:revert -d src/data-source.ts"
• Generate the initial migration from the current entity state and commit it:
  npm run migration:generate -- src/migrations/InitialSchema
• Ensure the initial migration runs cleanly against a fresh database: npm run migration:run
• Document in .env.example that migrations must be run manually after deployment

Files to Modify / Create

• backend/src/app.module.ts
• New: backend/src/data-source.ts
• New: backend/src/migrations/ (generated migration file)
• backend/package.json