fix: enable fallback auth methods for compatibility

Accept any password/key as fallback for clients that still try auth

src/shellmate/ssh/server.py

@@ -27,17 +27,25 @@ class ShellMateSSHServer(asyncssh.SSHServer):
     
     def begin_auth(self, username: str) -> bool:
         self._username = username
-        # Return False = auth complete (no auth required)
+        # Return False = auth complete immediately (no auth required)
-        # This allows instant passwordless connections
+        # This tells the SSH client that no authentication is needed
         return False
     
     def password_auth_supported(self) -> bool:
-        # Not needed since we skip auth entirely
+        # Enable password auth as fallback - accept any/empty password
-        return False
+        return True
+    
+    def validate_password(self, username: str, password: str) -> bool:
+        # Accept any password (including empty) for guest access
+        return True
     
     def public_key_auth_supported(self) -> bool:
-        # Not needed since we skip auth entirely
+        # Accept any public key
-        return False
+        return True
+    
+    def validate_public_key(self, username: str, key: asyncssh.SSHKey) -> bool:
+        # Accept any key for guest access
+        return True
 
 
 async def handle_client(process: asyncssh.SSHServerProcess) -> None: