Database: Initialize Core Schema and Service

[DocNR]

Component

Component: Database

Implementation Details

Core database schema implementation including:

• Create src/database directory structure
• Implement DbService class with SQLite configuration
• Set up schema versioning system
• Create initial tables (exercises, formats, tags)

Files to create:

src/
  └── database/
      ├── schema.ts        // Schema definitions & versioning
      ├── db-service.ts    // Core database service
      ├── migrations/      // Migration files
      │   └── 001_initial.ts  
      └── models/         // Type definitions
          ├── exercise.ts
          └── template.ts

### Acceptance Criteria

- [ ] Database service initialized with SQLite
- [ ] Schema version tracking implemented
- [ ] Core tables created with proper constraints 
- [ ] Basic CRUD operations working
- [ ] Test suite added
- [ ] Documentation added for schema

### Complexity

Medium (1-2 days)

### Additional Context

This is the foundation for all database operations. We need to ensure proper error handling and transaction support from the start.