docs: add AI code generation requirements and comprehensive Google-style docstrings

- Add AI code generation requirements to AGENTS.md
- Add module-level docstrings to all 46 Python modules
- Add detailed Google-style docstrings to all classes and functions
- Remove all inline comments following self-documenting code principle
- Include Args, Returns, Raises sections in function docstrings
- Add Attributes and Examples sections to class docstrings

app/application/use_cases/create_post.py

@@ -1,4 +1,8 @@
-"""Create post use case."""
+"""Create post use case.
+
+This module implements the use case for creating new blog posts.
+Handles slug generation, duplicate checking, and entity persistence.
+"""
 
 from app.application.dtos.post import CreatePostDTO, PostResponseDTO
 from app.application.interfaces import TransactionManager
@@ -8,28 +12,57 @@ from app.domain.repositories import PostRepository
 
 
 class CreatePostUseCase:
-    """Use case for creating a new blog post."""
+    """Use case for creating a new blog post.
+
+    Encapsulates the business logic for creating posts including
+    slug generation from title and duplicate slug detection.
+
+    Attributes:
+        _post_repo: Repository for post data access.
+        _tx_manager: Transaction manager for commit control.
+
+    Example:
+        >>> use_case = CreatePostUseCase(post_repo, tx_manager)
+        >>> result = await use_case.execute(dto)
+    """
 
     def __init__(
         self,
         post_repo: PostRepository,
         tx_manager: TransactionManager,
     ) -> None:
+        """Initialize use case with dependencies.
+
+        Args:
+            post_repo: Repository for post operations.
+            tx_manager: Transaction manager instance.
+        """
         self._post_repo = post_repo
         self._tx_manager = tx_manager
 
     async def execute(self, dto: CreatePostDTO) -> PostResponseDTO:
-        """Execute the use case."""
-        # Generate slug from title
+        """Execute the use case to create a new post.
+
+        Args:
+            dto: Data transfer object containing post creation data
+                including title, content, author ID, and optional tags.
+
+        Returns:
+            PostResponseDTO with created post data including generated ID and slug.
+
+        Raises:
+            AlreadyExistsException: If a post with the same slug exists.
+
+        Note:
+            Slug is automatically generated from the title.
+        """
         from app.domain.value_objects import Slug
 
         slug = Slug.from_title(dto.title)
 
-        # Check if slug already exists
         if await self._post_repo.slug_exists(slug.value):
             raise AlreadyExistsException(f"Post with slug '{slug.value}' already exists")
 
-        # Create domain entity
         post = Post.create(
             title_str=dto.title,
             content_str=dto.content,
@@ -37,16 +70,20 @@ class CreatePostUseCase:
             tags=dto.tags or [],
         )
 
-        # Persist entity
         await self._post_repo.add(post)
-
-        # Commit transaction
         await self._tx_manager.commit()
 
         return self._map_to_dto(post)
 
     def _map_to_dto(self, post: Post) -> PostResponseDTO:
-        """Map domain entity to response DTO."""
+        """Map domain entity to response DTO.
+
+        Args:
+            post: Domain post entity.
+
+        Returns:
+            PostResponseDTO with all post attributes.
+        """
         return PostResponseDTO(
             id=post.id,
             title=post.title.value,