📦 Build: Modernize Python packaging and Flask 3.x compatibility

Replace the 2013-era build system with modern Python packaging and fix
all compatibility issues for Flask 3.x on Python 3.14.

Packaging
---------
- Replace setup.py and distribute_setup.py with pyproject.toml (PEP 621)
- Update dependencies: Flask 3.x, PyYAML 6.x, feedparser 6.x
- Replace tornado with gunicorn for production serving
- Replace nose/flake8 with pytest/ruff for testing

Flask 3.x and Python 3 fixes
----------------------------
- Replace removed flask.ext.mako imports with flask_mako
- Replace unsafe yaml.load() with yaml.safe_load()
- Remove Python 2 __future__ imports
- Fix gravatar email encoding order for Python 3 unicode strings
- Simplify app.py by removing defunct Tornado/OpenShift code
- Fix ruff import sorting, exclude legacy scripts/ and ipynb/
- Skip YAML files at unexpected directory depth in participants

Assisted-by: Claude Opus 4.6 (1M context)
Signed-off-by: Justin Wheeler <[email protected]>

Author: justwheel

app.py

@@ -1,17 +1,4 @@
-import os
-
 from hflossk.site import app
-from tornado.wsgi import WSGIContainer
-from tornado.httpserver import HTTPServer
-from tornado.ioloop import IOLoop
 
 if __name__ == "__main__":
-    if 'OPENSHIFT_PYTHON_IP' in os.environ:
-        host = os.environ['OPENSHIFT_PYTHON_IP']
-        port = int(os.environ['OPENSHIFT_PYTHON_PORT'])
-        http_server = HTTPServer(WSGIContainer(app))
-        http_server.listen(port, address=host)
-        IOLoop.instance().start()
-    else:
-        app.debug = True
-        app.run(threaded=True)
+    app.run(debug=True)