feat: update reset thumbnail feature (#2854)

* update reset thumbnail feature

* consolidate supported thumbnail extensions into site config; remove dedicated API

* allow patching thumb ; remove Reset Thumbnail API

* fix code formatting

---------

Co-authored-by: Aaron Liu <abslant.liu@gmail.com>

pkg/filemanager/manager/metadata.go

@@ -97,6 +97,15 @@ var (
 			},
 		},
 		"dav": {},
+		// Allow manipulating thumbnail metadata via public PatchMetadata API
+		"thumb": {
+			// Only supported thumb metadata currently is thumb:disabled
+			dbfs.ThumbDisabledKey: func(ctx context.Context, m *manager, patch *fs.MetadataPatch) error {
+				// Presence of this key disables thumbnails; value is ignored.
+				// We allow both setting and removing this key.
+				return nil
+			},
+		},
 		customizeMetadataSuffix: {
 			iconColorMetadataKey: validateColor(false),
 			emojiIconMetadataKey: func(ctx context.Context, m *manager, patch *fs.MetadataPatch) error {

pkg/thumb/builtin.go

@@ -19,6 +19,10 @@ import (
 
 const thumbTempFolder = "thumb"
 
+// BuiltinSupportedExts lists file extensions supported by the built-in
+// thumbnail generator. Extensions are lowercased and do not include the dot.
+var BuiltinSupportedExts = []string{"jpg", "jpeg", "png", "gif"}
+
 // Thumb 缩略图
 type Thumb struct {
 	src image.Image