Improve error type specificity in repository implementations

Background

Gemini Code Assist review in PR #119 identified that repository implementations may return misleading error types for database failures. For example, returning InvalidDeviceError or NetworkError instead of more appropriate storage-specific errors.

Current Issue

When database operations fail, the error types don't accurately represent the actual failure:

• Database connection errors might return NetworkError
• Schema issues might return InvalidDeviceError
• Storage failures lack specific error types

Proposed Solution

1. Create specific error types for storage failures:

   • StorageError.ConnectionFailed
   • StorageError.SchemaError
   • StorageError.TransactionFailed
   • StorageError.ConstraintViolation

2. Update repository implementations to return accurate error types

3. Update tests to assert on specific error types

Example

// Current (misleading)
catch (e: SQLException) {
    Either.Left(SynchronizationError.InvalidDeviceError(...))
}

// Proposed (accurate)
catch (e: SQLException) {
    Either.Left(StorageError.DatabaseError(
        message = "Failed to access database",
        cause = e
    ))
}

Benefits

• Better debugging with accurate error information
• Clearer error handling in application layer
• More maintainable error recovery strategies

Related

• PR #119 - Where this was identified
• Follows Error Handling Guidelines in docs/guidelines/error-handling.md

Priority

Medium - Improves error clarity but doesn't affect functionality