_turn-sound: Turn-end sound + Quota overlay

DSH plugin `_turn-sound` (maintainer Buir5, category Client) implements turn-end reminders and RMB deduction/balance prompts as sounds and draggable floating layers in the top-left corner. The host side handles accounting and audio provision via Node, while the client features a 38px golden bell icon. Features include turn-end sound (non-streaming, once per round), deduction floating layers (10-second fade-out, position memory), quota ledger (monitors `assistant/message.usage` and converts to RMB based on unit price), balance calibration (prioritizes `deepseekAccount.getBalance()`), and custom audio (upload MP3/WAV or built-in). Installation is managed via profile dependencies and `cordis.patch.yml`; the `dsh plugin add` command is not provided. Configuration is written to `~/.dsh/turn-sound/config.json`. Only supports web clients; the client must be wrapped using `window.__ModuleLoader__.load`. The CNY amount is estimated.