[Feature]: Manual migration file generation and management

**Problem Statement:**
While auto-migration works for simple cases, production applications need:
- Controlled schema changes with review process
- Data transformation during migrations
- Rollback capabilities
- Migration history tracking

**Proposed Solution:**
Add migration CLI and infrastructure:

```bash
bun orm migration:generate AddUserEmailIndex
bun orm migration:run
bun orm migration:rollback
bun orm migration:status
```

**Generated Migration Example:**
```typescript
import { Migration } from 'bun-sqlite-orm';

export class AddUserEmailIndex1234567890 implements Migration {
async up(db: Database): Promise {
await db.exec('CREATE INDEX idx_users_email ON users(email)');
}

async down(db: Database): Promise {
await db.exec('DROP INDEX idx_users_email');
}
}
```

**Features:**
- CLI for migration management
- Migration file templates
- Up/down migration execution
- Migration history table
- Schema diffing for auto-generation

Start by examining the proposed migration CLI commands and the generated TypeScript Migration example. Define the scope for generation, up/down execution, rollback, status tracking, and schema diffing before implementing. Done means the requested migration-management workflow is supported with migration history and reversible operations.

Written by the indexing model from the issue text.