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__,
+        }