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/entities/base.py

@@ -1,4 +1,9 @@
-"""Base entity for DDD domain layer."""
+"""Base entity for DDD domain layer.
+
+This module provides the foundational BaseEntity class that all domain
+entities must inherit from. It implements common entity patterns including
+identity management, equality comparison, and timestamp tracking.
+"""
 
 from abc import ABC, abstractmethod
 from dataclasses import dataclass, field
@@ -9,25 +14,62 @@ from uuid import UUID, uuid4
 
 @dataclass(kw_only=True)
 class BaseEntity(ABC):
-    """Base class for all domain entities."""
+    """Base class for all domain entities.
+
+    Provides common functionality for domain entities including unique
+    identification, creation/update timestamps, and equality comparison
+    based on identity.
+
+    Attributes:
+        id: Unique identifier for the entity, automatically generated.
+        created_at: Timestamp when the entity was created.
+        updated_at: Timestamp when the entity was last updated.
+
+    Example:
+        >>> class User(BaseEntity):
+        ...     name: str
+        ...     def to_dict(self) -> dict[str, Any]:
+        ...         return {"id": str(self.id), "name": self.name}
+    """
 
     id: UUID = field(default_factory=uuid4)
     created_at: datetime = field(default_factory=lambda: datetime.now(UTC))
     updated_at: datetime = field(default_factory=lambda: datetime.now(UTC))
 
     def __eq__(self, other: object) -> bool:
+        """Compare entities by identity.
+
+        Args:
+            other: Another object to compare with.
+
+        Returns:
+            True if both objects are BaseEntity instances with same ID.
+        """
         if not isinstance(other, BaseEntity):
             return NotImplemented
         return self.id == other.id
 
     def __hash__(self) -> int:
+        """Get hash based on entity identity.
+
+        Returns:
+            Hash of the entity ID.
+        """
         return hash(self.id)
 
     def touch(self) -> None:
-        """Update the updated_at timestamp."""
+        """Update the updated_at timestamp.
+
+        Should be called whenever the entity is modified to track
+        the last modification time.
+        """
         self.updated_at = datetime.now(UTC)
 
     @abstractmethod
     def to_dict(self) -> dict[str, Any]:
-        """Convert entity to dictionary."""
+        """Convert entity to dictionary representation.
+
+        Returns:
+            Dictionary containing all entity attributes.
+        """
         ...