Add OpenRGB per-zone LED control with separate/combined modes and zone preview

- Zone picker UI in device add/settings modals with per-zone checkbox selection
- Combined mode: pixels distributed sequentially across zones
- Separate mode: full effect resampled independently to each zone via linear interpolation
- Per-zone LED preview in target cards: one canvas strip per zone with hover overlay labels
- Zone badges on device cards enriched with actual LED counts from OpenRGB API
- Fix stale led_count by using device_led_count discovered at connect time

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

server/src/wled_controller/static/locales/en.json

@@ -137,6 +137,15 @@
   "device.ws_url.hint": "WebSocket URL for clients to connect and receive LED data",
   "device.openrgb.url": "OpenRGB URL:",
   "device.openrgb.url.hint": "OpenRGB server address (e.g. openrgb://localhost:6742/0)",
+  "device.openrgb.zone": "Zones:",
+  "device.openrgb.zone.hint": "Select which LED zones to control (leave all unchecked for all zones)",
+  "device.openrgb.zone.loading": "Loading zones…",
+  "device.openrgb.zone.error": "Failed to load zones",
+  "device.openrgb.mode": "Zone mode:",
+  "device.openrgb.mode.hint": "Combined treats all zones as one continuous LED strip. Separate renders each zone independently with the full effect.",
+  "device.openrgb.mode.combined": "Combined strip",
+  "device.openrgb.mode.separate": "Independent zones",
+  "device.openrgb.added_multiple": "Added {count} devices",
   "device.type.openrgb": "OpenRGB",
   "device.url.hint": "IP address or hostname of the device (e.g. http://192.168.1.100)",
   "device.name": "Device Name:",