fix: enable zero-auth SSH connections

- Return False from begin_auth to skip authentication
- Users can connect instantly without password/key prompts
- Frictionless: just ssh play@shellmate.sh

src/shellmate/ssh/server.py

@@ -27,23 +27,17 @@ class ShellMateSSHServer(asyncssh.SSHServer):
     
     def begin_auth(self, username: str) -> bool:
         self._username = username
-        # Allow all usernames, we'll handle auth in the app
-        return True
+        # Return False = auth complete (no auth required)
+        # This allows instant passwordless connections
+        return False
     
     def password_auth_supported(self) -> bool:
-        return True
-    
-    def validate_password(self, username: str, password: str) -> bool:
-        # Guest access - accept any password or empty
-        # For registered users, validate against database
-        return True  # TODO: Implement proper auth
+        # Not needed since we skip auth entirely
+        return False
     
     def public_key_auth_supported(self) -> bool:
-        return True
-    
-    def validate_public_key(self, username: str, key: asyncssh.SSHKey) -> bool:
-        # Accept any public key for now
-        return True  # TODO: Implement key-based auth
+        # Not needed since we skip auth entirely
+        return False
 
 
 async def handle_client(process: asyncssh.SSHServerProcess) -> None: