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/get_post.py

@@ -1,4 +1,8 @@
-"""Get post use case."""
+"""Get post use case.
+
+This module implements the use case for retrieving blog posts.
+Supports lookup by both ID and slug.
+"""
 
 from uuid import UUID
 
@@ -10,32 +14,78 @@ from app.domain.repositories import PostRepository
 
 
 class GetPostUseCase:
-    """Use case for retrieving a post by ID or slug."""
+    """Use case for retrieving a post by ID or slug.
+
+    Provides methods to fetch posts using different identifiers.
+    Handles not-found scenarios with appropriate exceptions.
+
+    Attributes:
+        _post_repo: Repository for post data access.
+        _tx_manager: Transaction manager for transaction control.
+
+    Example:
+        >>> use_case = GetPostUseCase(post_repo, tx_manager)
+        >>> post = await use_case.by_id(post_id)
+        >>> post = await use_case.by_slug("my-post")
+    """
 
     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 by_id(self, post_id: UUID) -> PostResponseDTO:
-        """Get post by ID."""
+        """Get post by ID.
+
+        Args:
+            post_id: Unique identifier of the post.
+
+        Returns:
+            PostResponseDTO with complete post data.
+
+        Raises:
+            NotFoundException: If post with given ID does not exist.
+        """
         post = await self._post_repo.get_by_id(post_id)
         if not post:
             raise NotFoundException(f"Post with id '{post_id}' not found")
         return self._map_to_dto(post)
 
     async def by_slug(self, slug: str) -> PostResponseDTO:
-        """Get post by slug."""
+        """Get post by slug.
+
+        Args:
+            slug: URL-friendly slug identifier.
+
+        Returns:
+            PostResponseDTO with complete post data.
+
+        Raises:
+            NotFoundException: If post with given slug does not exist.
+        """
         post = await self._post_repo.get_by_slug(slug)
         if not post:
             raise NotFoundException(f"Post with slug '{slug}' not found")
         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,