feat: add SRP authentication, improve security

- Replace RSA key exchange with SRP (Secure Remote Password)
- Password never transmitted over network
- Add unit tests for endpoints
- Fix datetime.UTC compatibility for Python < 3.11
- Fix logger.exception usage
- Update README with new auth flow diagram

cmd_chat/server/server.py

@@ -2,22 +2,20 @@ from typing import Optional
 from .logger import logger
 from .factory import create_app
 
-app = create_app()
-
 
 def run_server(
     host: str = "0.0.0.0",
     port: int = 8000,
-    admin_password: Optional[str] = None,
+    password: Optional[str] = None,
     workers: int = 1,
 ) -> None:
-    app.ctx.admin_password = admin_password
+    app = create_app(password=password or "")
     logger.info(f"Starting server on {host}:{port}")
 
     app.run(
         host=host,
         port=port,
-        workers=workers,
+        single_process=True,
         debug=False,
         access_log=True,
     )