Enhanced Migration System with Foreign Keys, Indexes, and Batch Support

[wilburhimself]

This PR significantly enhances Theory's migration system with robust features for managing complex database schemas.

Key Features:

• Foreign key support with configurable ON DELETE/UPDATE actions
• Index management including unique constraints
• Batch migrations with transaction support
• Improved error handling and SQLite type validation
• Migration status tracking and rollback capabilities

Technical Changes:

• Added ForeignKey and Index structs to support table relationships and optimizations
• Implemented transaction support in Up/Down operations for atomic migrations
• Enhanced error handling with descriptive messages
• Added validation for SQLite column types
• Improved migrations table initialization and status tracking
• Added comprehensive test coverage for all new features

Documentation:

• Updated README with detailed migration examples
• Added documentation for all supported operations
• Included examples of foreign keys, indexes, and batch migrations
• Added section describing migration features and available operations

Breaking Changes: None

Testing:
All tests pass, including new test cases for:

• Foreign key operations
• Index management
• Batch migrations with transactions
• Error handling scenarios
• Migration status tracking