feat(webdav): follow-up 补齐自动同步与大文件防护 (#1043)

* feat(webdav): add robust auto sync with failure feedback

(cherry picked from commit bb6760124a62a964b36902c004e173534910728f)

* fix(webdav): enforce bounded download and extraction size

(cherry picked from commit 7777d6ec2b9bba07c8bbba9b04fe3ea6b15e0e79)

* fix(webdav): only show auto-sync callout for auto-source errors

* refactor(webdav): remove services->commands auto-sync dependency

src/lib/schemas/settings.ts

@@ -33,6 +33,7 @@ export const settingsSchema = z.object({
   webdavSync: z
     .object({
       enabled: z.boolean().optional(),
+      autoSync: z.boolean().optional(),
       baseUrl: z.string().trim().optional().or(z.literal("")),
       username: z.string().trim().optional().or(z.literal("")),
       password: z.string().optional(),
@@ -42,6 +43,7 @@ export const settingsSchema = z.object({
         .object({
           lastSyncAt: z.number().nullable().optional(),
           lastError: z.string().nullable().optional(),
+          lastErrorSource: z.string().nullable().optional(),
           lastRemoteEtag: z.string().nullable().optional(),
           lastLocalManifestHash: z.string().nullable().optional(),
           lastRemoteManifestHash: z.string().nullable().optional(),