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/infrastructure/repositories/post.py

@@ -10,9 +10,10 @@ from sqlalchemy import or_, select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.domain.entities import Post
+from app.domain.entities.like import PostLike
 from app.domain.repositories import PostRepository
 from app.domain.value_objects import Content, Slug, Title
-from app.infrastructure.database.models import PostORM
+from app.infrastructure.database.models import PostLikeORM, PostORM
 
 
 class SQLAlchemyPostRepository(PostRepository):
@@ -53,6 +54,7 @@ class SQLAlchemyPostRepository(PostRepository):
             slug=Slug(orm.slug),
             author_id=orm.author_id,
             published=orm.published,
+            like_count=orm.like_count,
             tags=orm.tags or [],
             created_at=orm.created_at,
             updated_at=orm.updated_at,
@@ -74,6 +76,7 @@ class SQLAlchemyPostRepository(PostRepository):
             slug=post.slug.value,
             author_id=post.author_id,
             published=post.published,
+            like_count=post.like_count,
             tags=post.tags,
             created_at=post.created_at,
             updated_at=post.updated_at,
@@ -124,6 +127,7 @@ class SQLAlchemyPostRepository(PostRepository):
         orm.content = entity.content.value
         orm.slug = entity.slug.value
         orm.published = entity.published
+        orm.like_count = entity.like_count
         orm.tags = entity.tags
         orm.updated_at = entity.updated_at
 
@@ -284,3 +288,60 @@ class SQLAlchemyPostRepository(PostRepository):
         result = await self._session.execute(stmt)
         orms = result.scalars().all()
         return [self._to_domain(orm) for orm in orms]
+
+    async def get_like(self, post_id: UUID, liked_by: str) -> PostLike | None:
+        """Get a like by post and user/device.
+
+        Args:
+            post_id: UUID of the post.
+            liked_by: User ID or device ID.
+
+        Returns:
+            PostLike if found, None otherwise.
+        """
+        result = await self._session.execute(
+            select(PostLikeORM).where(
+                PostLikeORM.post_id == str(post_id),
+                PostLikeORM.liked_by == liked_by,
+            )
+        )
+        orm = result.scalar_one_or_none()
+        if not orm:
+            return None
+        return PostLike(
+            id=UUID(orm.id),
+            post_id=UUID(orm.post_id),
+            liked_by=orm.liked_by,
+            created_at=orm.created_at,
+        )
+
+    async def add_like(self, like: PostLike) -> None:
+        """Add a new like.
+
+        Args:
+            like: PostLike entity to add.
+        """
+        orm = PostLikeORM(
+            id=str(like.id),
+            post_id=str(like.post_id),
+            liked_by=like.liked_by,
+            created_at=like.created_at,
+        )
+        self._session.add(orm)
+
+    async def remove_like(self, post_id: UUID, liked_by: str) -> None:
+        """Remove a like by post and user/device.
+
+        Args:
+            post_id: UUID of the post.
+            liked_by: User ID or device ID.
+        """
+        result = await self._session.execute(
+            select(PostLikeORM).where(
+                PostLikeORM.post_id == str(post_id),
+                PostLikeORM.liked_by == liked_by,
+            )
+        )
+        orm = result.scalar_one_or_none()
+        if orm:
+            await self._session.delete(orm)