fix(api): degrade recent event readback failures

apps/api/src/api/v1/platform/events.py

@@ -118,6 +118,8 @@ class RecentEventsResponse(BaseModel):
     events: list[ChannelEventItem]
     total: int
     limit: int
+    source_status: str = "ready"
+    source_error: str | None = None
 
 
 class ChannelEventDossierItem(BaseModel):
@@ -667,9 +669,26 @@ async def list_recent_events(
     ),
     limit: int = Query(20, ge=1, le=100, description="最多返回筆數"),
 ) -> dict[str, Any]:
-    return await list_recent_channel_events(
-        project_id=project_id,
-        channel_type=channel_type,
-        provider_prefix=provider_prefix,
-        limit=limit,
-    )
+    try:
+        return await list_recent_channel_events(
+            project_id=project_id,
+            channel_type=channel_type,
+            provider_prefix=provider_prefix,
+            limit=limit,
+        )
+    except Exception as exc:
+        logger.warning(
+            "recent_channel_events_source_unavailable",
+            project_id=project_id or "awoooi",
+            channel_type=channel_type,
+            provider_prefix=provider_prefix,
+            limit=limit,
+            error=exc.__class__.__name__,
+        )
+        return {
+            "events": [],
+            "total": 0,
+            "limit": max(1, min(limit, 100)),
+            "source_status": "source_unavailable",
+            "source_error": exc.__class__.__name__,
+        }

apps/api/tests/test_platform_events_project_context.py

@@ -10,6 +10,33 @@ from src.core.context import (
 )
 
 
+@pytest.mark.asyncio
+async def test_recent_events_degrades_when_source_unavailable(monkeypatch):
+    async def fake_list_recent_channel_events(**kwargs):
+        raise RuntimeError("db unavailable")
+
+    monkeypatch.setattr(
+        events,
+        "list_recent_channel_events",
+        fake_list_recent_channel_events,
+    )
+
+    response = await events.list_recent_events(
+        project_id="awoooi",
+        channel_type=None,
+        provider_prefix="alertmanager",
+        limit=20,
+    )
+
+    assert response == {
+        "events": [],
+        "total": 0,
+        "limit": 20,
+        "source_status": "source_unavailable",
+        "source_error": "RuntimeError",
+    }
+
+
 @pytest.mark.asyncio
 async def test_source_correlation_review_uses_body_project_context(monkeypatch):
     observed: dict[str, object] = {}