[What's New Analysis] Create first-party Python hosting documentation

Summary

The first-party Aspire.Hosting.Python package introduced in Aspire 13.0 has no standalone documentation. The existing python-integration doc covers the Community Toolkit package (CommunityToolkit.Aspire.Hosting.Python.Extensions), not the first-party package.

What's Missing

The following APIs are documented only in what's-new-in-aspire-13:

// These are in Aspire.Hosting.Python - NOT the Community Toolkit
builder.AddPythonApp("etl-job", "../etl", "process_data.py");
builder.AddPythonModule("celery-worker", "../worker", "celery");
builder.AddPythonExecutable("api", "../api", "gunicorn");
builder.AddUvicornApp("api", "./api", "main:app");

// Package management
.WithUv()   // uv package manager
.WithPip()  // pip package manager
.WithVirtualEnvironment(".venv", createIfNotExists: true)

Suggested Content

1. Hosting integration section with all 4 app types
2. Package management - WithUv vs WithPip, auto-detection behavior
3. Virtual environment configuration - paths, auto-creation
4. Dockerfile generation - automatic multi-stage builds
5. Python version detection - .python-version, pyproject.toml, fallback
6. VS Code debugging - breakpoints work automatically
7. Examples - FastAPI, Flask, Celery worker patterns

Why It Matters

Python is now a "first-class citizen" in Aspire 13 - this is a major selling point. Users searching for "Aspire Python" find the Community Toolkit doc which uses different APIs.