Add Chinese locale, fix audio device duplicates, remove display lock restriction

- Add Simplified Chinese (中文) locale with all 906 translation keys
- Fix duplicate audio devices: WASAPI two-pass enumerate avoids double-listing
  loopback endpoints; cross-engine dedup by (name, is_loopback) prefers
  higher-priority engine
- Remove redundant display lock check from capture template, picture source,
  and postprocessing template test endpoints — screen capture is read-only
  and concurrent access is safe

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -51,7 +51,7 @@ A Home Assistant integration exposes devices as entities for smart home automati
 - Visual calibration editor with overlay preview
 - Live LED strip preview via WebSocket
 - Real-time FPS, latency, and uptime charts
-- Localized in English and Russian
+- Localized in English, Russian, and Chinese
 
 ### Home Assistant Integration
 
@@ -113,7 +113,7 @@ wled-screen-controller/
 │   │   │   ├── js/core/             # API client, state, i18n, modals, events
 │   │   │   ├── js/features/         # Feature modules (devices, streams, targets, etc.)
 │   │   │   ├── css/                 # Stylesheets
-│   │   │   └── locales/             # en.json, ru.json
+│   │   │   └── locales/             # en.json, ru.json, zh.json
 │   │   └── utils/                   # Logging, monitor detection
 │   ├── config/                      # default_config.yaml
 │   ├── tests/                       # pytest suite