refactor(validation): improve rule injection flow

[mosha99]

This PR refactors the validation infrastructure to improve readability,
reduce unnecessary object instantiation, and minimize reflection usage,
while preserving existing behavior.

Key changes

1. Refactored RegisterValidatorsAsServices

   • Simplified the registration logic for better readability
   • Removed the need to instantiate objects solely for applying validation rules
   • Introduced a generic static helper method and invoked it via reflection,
     reducing overall reflection usage and improving maintainability

2. Updated ValidateApplicationModel

   • Changed from a regular interface method to a static abstract method
   • Allows invocation without creating new instances
   • Enables cleaner switching logic inside generic methods

3. Updated implementations of IValidatableModel

   • Aligned all implementing types with the new static abstract contract
   • No behavioral changes in validation results

Notes

• No breaking changes in public behavior
• Focused on internal refactoring and performance/readability improvements

[babaktaremi]

Hi, thanks for your contribution! Overall, it looks good, but there are still some important improvements from previous versions that haven’t been addressed. Refactoring those would make a significant impact.