Add project logo to README and documentation

Add PyAthena logo (owl with Athena helmet and Python snake) generated
with Nano-Banana Pro (Gemini 3 Pro Image). The logo is displayed in the
Furo theme sidebar for documentation and at the top of the README.

- Add transparent PNG logo to docs/_static/logo.png
- Add logo image and Nano-Banana Pro attribution to README.rst
- Configure html_logo in docs/conf.py for Furo sidebar display
- Add custom CSS for sidebar logo styling

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: laughingman7743

README.rst

@@ -17,6 +17,11 @@
   :target: https://mypy-lang.org/
   :alt: mypy
 
+.. image:: docs/_static/logo.png
+  :alt: PyAthena logo
+  :align: center
+  :width: 200
+
 PyAthena
 ========
 
@@ -99,3 +104,8 @@ Links
 - PyPI Releases: https://pypi.org/project/PyAthena/
 - Source Code: https://github.com/laughingman7743/PyAthena/
 - Issue Tracker: https://github.com/laughingman7743/PyAthena/issues
+
+Logo
+----
+
+The PyAthena logo was generated using `Nano-Banana Pro <https://deepmind.google/models/gemini-image/pro/>`_ (Gemini 3 Pro Image).

docs/_static/logo.png

@@ -162,6 +162,7 @@ def setup(app):
 # https://www.sphinx-doc.org/en/master/usage/configuration.html#options-for-html-output
 
 html_theme = "furo"
+html_logo = "_static/logo.png"
 html_static_path = ["_static"]
 html_css_files = [
     "custom.css",