feat(automation): add retry policy helper

surfsense_backend/app/automations/runtime/retries.py

@@ -0,0 +1,36 @@
+"""Retry policy enforcement for action handlers."""
+
+from __future__ import annotations
+
+import asyncio
+from collections.abc import Awaitable, Callable
+
+
+async def with_retries[T](
+    coro_factory: Callable[[], Awaitable[T]],
+    *,
+    max_retries: int,
+    backoff: str,
+    timeout: int | None,
+) -> tuple[T, int]:
+    """Call ``coro_factory`` up to ``1 + max_retries`` times. Return ``(result, attempts)``."""
+    total = 1 + max(0, max_retries)
+    for attempt in range(1, total + 1):
+        try:
+            coro = coro_factory()
+            if timeout is not None and timeout > 0:
+                return await asyncio.wait_for(coro, timeout=timeout), attempt
+            return await coro, attempt
+        except Exception:
+            if attempt >= total:
+                raise
+            await asyncio.sleep(_backoff_seconds(backoff, attempt))
+    raise RuntimeError("with_retries exhausted without raising or returning")
+
+
+def _backoff_seconds(strategy: str, attempt: int) -> float:
+    if strategy == "exponential":
+        return float(2 ** (attempt - 1))
+    if strategy == "linear":
+        return float(attempt)
+    return 0.0