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/domain/__init__.py

@@ -1,4 +1,8 @@
-"""Domain layer exports."""
+"""Domain layer exports.
+
+This module re-exports all domain layer components including
+entities, value objects, repositories, and exceptions.
+"""
 
 from app.domain.entities import BaseEntity, Post
 from app.domain.exceptions import (
@@ -13,18 +17,14 @@ from app.domain.repositories import PostRepository, Repository
 from app.domain.value_objects import Content, Slug, Title, ValueObject
 
 __all__ = [
-    # Entities
     "BaseEntity",
     "Post",
-    # Value Objects
     "ValueObject",
     "Title",
     "Content",
     "Slug",
-    # Repositories
     "Repository",
     "PostRepository",
-    # Exceptions
     "DomainException",
     "ValidationException",
     "NotFoundException",