List Memory Proposals

List the user's proposals (default status=pending). Each carries current_body/current_hash of the live target slug so the SPA can render a before/after diff.

?status= filters by status ('all' = any status). ?session_id= scopes to one conversation's session-origin proposals (the "为当前对话生成记忆" review pane) — both filters compose, so the SPA asks for ?session_id=<id>&status=pending to drive the red-dot count.