feat(organize): separate source dir from destination dir (从源目录整理到目的地目录)

Previously organize only exposed a single 'target dir' that was actually
the destination, conflating 源目录 (where files to organize live) with
目的地目录 (where organized files go). Add an explicit source directory:

- OrganizeOptions gains SourcePath; DestPath replaces the old TargetPath
  (destination) for clarity. New organize.source_dir setting + source_path
  request override; resolveSourceRoot falls back to library path.
- OrganizeLibraryWithOptions only organizes media located under the source
  root, so operators can point at a specific download/staging folder and
  organize into a distinct destination.
- Handler accepts source_path/dest_path (target_path kept as a deprecated
  alias for the destination, backward compatible).
- Settings page splits into 整理源目录(待整理) + 整理目的地目录; Tools organize
  panel exposes 源目录 + 目的地目录 inputs with clear copy.

Defaults are unchanged (source = destination = library path) so existing
setups behave identically. Adds a regression test that organize is scoped
to the source directory.

Co-Authored-By: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

web/src/api/tools.ts

@@ -5,8 +5,10 @@ import { api } from './client'
 // dispatching a test notification through the configured channels.
 // OrganizeOverrides are optional single-request overrides for an organize
 // action. Empty fields fall back to the system settings.
+// source_path = 源目录（待整理文件所在），dest_path = 目的地目录（整理输出到哪里）。
 export interface OrganizeOverrides {
-  target_path?: string
+  source_path?: string
+  dest_path?: string
   transfer_mode?: string
 }