Add and update docstrings for profile services and schema

Added or revised concise, PEP 257-compliant docstrings for all public classes and methods in profile export/import services, router endpoints, exceptions, and MFA schema. Updated docstring formats to match new repository guidelines, clarified argument and return value descriptions, and removed extended explanations and examples. Also updated .github/copilot-instructions.md with new Python code style and docstring requirements.

.github/copilot-instructions.md

@@ -132,4 +132,68 @@ Repository root:
 - **Authentication**: JWT tokens with 15-minute access tokens
 - **Deployment**: Docker containers with multi-stage builds
 
-Always prioritize frontend development workflow for UI changes and use Docker for full-stack development.
+Always prioritize frontend development workflow for UI changes and use Docker for full-stack development.
+
+## Task Execution Guidelines
+- **Do ONLY what is explicitly requested** - do not add extra 
+  documentation, summaries, or "helpful" files unless specifically 
+  asked.
+- If asked to implement a feature, implement ONLY that feature - no 
+  additional documentation beyond code comments.
+- Do not create README files, summary documents, quick reference 
+  guides, or completion reports unless explicitly requested.
+- When implementing changes, focus on the code implementation itself, 
+  not supplementary documentation.
+- Ask for clarification if the scope is unclear rather than assuming 
+  additional deliverables are wanted.
+
+## Python Code Style Requirements
+
+### Modern Python Syntax (Python 3.13+)
+- Use modern type hint syntax: `int | None`, `list[str]`, 
+  `dict[str, Any]`
+- Do NOT use `typing.Optional`, `typing.List`, `typing.Dict`, etc.
+- Target Python 3.13+ features and syntax
+
+### PEP 8 Line Limits
+- Code lines: **79 characters maximum**
+- Comments and docstrings: **72 characters maximum**
+- Enforce strictly - no exceptions
+
+### Docstring Standard (PEP 257)
+- **Always follow PEP 257** with Args/Returns/Raises sections
+- **Format**: One-line summary, blank line, then 
+  Args/Returns/Raises sections
+- **Always include Args/Returns/Raises** even when parameters seem 
+  obvious
+- **NO examples** in docstrings - keep in external docs or tests
+- **NO extended explanations** - one-line summary + sections only
+- **Keep concise** - describe what, not how
+
+**Function docstring format:**
+```python
+def function(param: str) -> int:
+    """
+    One-line summary of what this does.
+
+    Args:
+        param: Description of param.
+
+    Returns:
+        Description of return value.
+
+    Raises:
+        ValueError: When param is invalid.
+    """
+```
+
+**Class docstring format:**
+```python
+class MyClass:
+    """
+    One-line summary of the class.
+
+    Attributes:
+        attr: Description of attribute.
+    """
+```