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/value_objects/content.py

@@ -1,4 +1,8 @@
-"""Content value object."""
+"""Content value object.
+
+This module defines the Content value object for blog post content
+with validation for minimum and maximum length constraints.
+"""
 
 from dataclasses import dataclass
 
@@ -7,12 +11,35 @@ from app.domain.value_objects.base import ValueObject
 
 @dataclass(frozen=True, slots=True)
 class Content(ValueObject[str]):
-    """Blog post content value object."""
+    """Blog post content value object.
+
+    Wraps and validates blog post content ensuring it meets length
+    requirements and is not empty.
+
+    Attributes:
+        value: The content string value.
+        MIN_LENGTH: Minimum allowed content length (10 characters).
+        MAX_LENGTH: Maximum allowed content length (50000 characters).
+
+    Raises:
+        ValueError: If content is empty, too short, or too long.
+
+    Example:
+        >>> content = Content("This is valid content...")
+        >>> print(content.value)
+    """
 
     MIN_LENGTH: int = 10
     MAX_LENGTH: int = 50000
 
     def _validate(self) -> None:
+        """Validate content string.
+
+        Checks that content is a non-empty string within length bounds.
+
+        Raises:
+            ValueError: If content fails validation criteria.
+        """
         if not isinstance(self.value, str):
             raise ValueError("Content must be a string")
         if not self.value.strip():