feat: add like/unlike toggle on blog posts with per-user tracking

- PostLike domain entity (post_id, liked_by) with BaseEntity integration
- Post entity: add like_count field (default 0) and to_dict serialization
- PostRepository interface: add get_like, add_like, remove_like methods
- TogglePostLikeUseCase: toggle logic (like → unlike, unlike → like)
- PostResponseDTO/PostResponseSchema: add like_count field
- PostLikeORM model with FK to posts and cascade delete
- SQLAlchemyPostRepository: implement like query/add/remove with ORM mapping
- DI provider registration for TogglePostLikeUseCase
- API endpoint POST /api/v1/posts/{id}/like (auth required)
- Unit tests: PostLike entity, Post.like_count, TogglePostLikeUseCase (7 tests)
- API tests: POST /api/v1/posts/{id}/like (4 tests)
- Test model files: FEATURE_LIKES.md, TEST_MODEL.md updated

app/presentation/api/deps.py

@@ -16,6 +16,7 @@ from app.application import (
     GetPostUseCase,
     ListPostsUseCase,
     PublishPostUseCase,
+    TogglePostLikeUseCase,
     UpdatePostUseCase,
 )
 from app.domain.exceptions import ForbiddenException, UnauthorizedException
@@ -28,6 +29,7 @@ UpdatePostDep = FromDishka[UpdatePostUseCase]
 DeletePostDep = FromDishka[DeletePostUseCase]
 ListPostsDep = FromDishka[ListPostsUseCase]
 PublishPostDep = FromDishka[PublishPostUseCase]
+ToggleLikeDep = FromDishka[TogglePostLikeUseCase]
 
 security = HTTPBearer(auto_error=False)