add safe home assistant error handling

app/ha/exceptions.py

@@ -0,0 +1,27 @@
+from __future__ import annotations
+
+
+class HaClientError(Exception):
+    """Base class for Home Assistant integration failures."""
+
+    public_detail = "Home Assistant is currently unavailable."
+
+
+class HaTimeoutError(HaClientError):
+    public_detail = "Home Assistant request timed out."
+
+
+class HaHttpError(HaClientError):
+    public_detail = "Home Assistant returned an error."
+
+    def __init__(self, status_code: int, message: str | None = None) -> None:
+        super().__init__(message or self.public_detail)
+        self.status_code = status_code
+
+
+class HaAuthError(HaHttpError):
+    public_detail = "Home Assistant authentication failed."
+
+
+class HaUnexpectedPayloadError(HaClientError):
+    public_detail = "Home Assistant returned an unexpected response."