Handle invalid random photos before device writes and trace selections

docs/PHOTO_SOURCES.md

@@ -151,3 +151,13 @@ This optional integration reads the existing shared-space People catalog. It doe
 已有数据源 `orientation=null` 保持原来的全部方向，编辑器显示“不筛方向（原有设置）”；新建数据源默认自动。尺寸缓存持久化在 SQLite `photo_dimensions`，按路径、修改时间和大小失效。首次扫描读取本地图片尺寸和 EXIF，不批量生成全图库预览；后续刷新复用缓存。仅 NAS 本地源支持，WebDAV 不批量下载原图测尺寸。自动模式读取统一 Device Model，不依赖 KoKonna 私有字段；90°/270° 交换宽高。
 
 Orientation options: landscape, portrait, auto. Auto follows the target device dimensions and rotation (90°/270° swap width and height). Manual direction controls both selection and rendering. Photo and caption layouts support landscape and portrait. Classification honors EXIF orientation; square photos are excluded from directional matches. Existing sources remain unfiltered (`null`) until changed. Dimensions persist in SQLite and refresh when the file changes. Local NAS sources only; no bulk original downloads from WebDAV. Empty matches fail closed. This controls selection, not photo rotation or stretching.
+
+### Invalid photos and selection tracing
+
+Local catalogs share the renderer's 25-million-pixel limit. Oversized originals
+use an existing Synology XL preview when enabled and available; otherwise they
+are excluded. Header-only catalog inspection does not guarantee full decoding.
+Random rendering tries at most five distinct candidates before any device write,
+skipping only invalid or unavailable images. Explicit selections never fall back.
+Operation `result.photo_attempts` records source-relative item IDs, names, status
+and stable error codes, including failures. This does not retry upload or switch.

docs/openapi.json

@@ -10734,6 +10734,16 @@
       },
       "OperationResult": {
         "properties": {
+          "photo_attempts": {
+            "items": {
+              "additionalProperties": {
+                "type": "string"
+              },
+              "type": "object"
+            },
+            "type": "array",
+            "title": "Photo Attempts"
+          },
           "image_id": {
             "anyOf": [
               {