Simplify calibration model, add pixel preview, and improve UI

- Replace segment-based calibration with core parameters (leds_top/right/bottom/left);
  segments are now derived at runtime via lookup tables
- Fix clockwise/counterclockwise edge traversal order for all 8 start_position/layout
  combinations (e.g. bottom_left+clockwise now correctly goes up-left first)
- Add pixel layout preview overlay with color-coded edges, LED index labels,
  direction arrows, and start position marker
- Move "Add New Device" form into a modal dialog triggered by "+" button
- Add display index selector to device settings modal
- Migrate from requirements.txt to pyproject.toml for dependency management
- Update Dockerfile and docs to use `pip install .`

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

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

@@ -77,6 +77,8 @@
   "settings.brightness": "Brightness:",
   "settings.brightness.hint": "Global brightness for this WLED device (0-100%)",
   "settings.url.hint": "IP address or hostname of your WLED device",
+  "settings.display_index": "Display:",
+  "settings.display_index.hint": "Which screen to capture for this device",
   "settings.button.cancel": "Cancel",
   "settings.health_interval": "Health Check Interval (s):",
   "settings.health_interval.hint": "How often to check the WLED device status (5-600 seconds)",
@@ -106,6 +108,17 @@
   "calibration.button.save": "Save",
   "calibration.saved": "Calibration saved successfully",
   "calibration.failed": "Failed to save calibration",
+  "preview.title": "Pixel Layout Preview",
+  "preview.button": "Preview",
+  "preview.start": "START",
+  "preview.offset_leds": "Offset: {count} LEDs",
+  "preview.direction.cw": "Clockwise",
+  "preview.direction.ccw": "Counterclockwise",
+  "preview.edge.top": "Top",
+  "preview.edge.right": "Right",
+  "preview.edge.bottom": "Bottom",
+  "preview.edge.left": "Left",
+  "preview.no_calibration": "No calibration data. Please calibrate the device first.",
   "server.healthy": "Server online",
   "server.offline": "Server offline",
   "error.unauthorized": "Unauthorized - please login",

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

@@ -77,6 +77,8 @@
   "settings.brightness": "Яркость:",
   "settings.brightness.hint": "Общая яркость для этого WLED устройства (0-100%)",
   "settings.url.hint": "IP адрес или имя хоста вашего WLED устройства",
+  "settings.display_index": "Дисплей:",
+  "settings.display_index.hint": "Какой экран захватывать для этого устройства",
   "settings.button.cancel": "Отмена",
   "settings.health_interval": "Интервал Проверки (с):",
   "settings.health_interval.hint": "Как часто проверять статус WLED устройства (5-600 секунд)",
@@ -106,6 +108,17 @@
   "calibration.button.save": "Сохранить",
   "calibration.saved": "Калибровка успешно сохранена",
   "calibration.failed": "Не удалось сохранить калибровку",
+  "preview.title": "Предпросмотр Расположения Пикселей",
+  "preview.button": "Предпросмотр",
+  "preview.start": "СТАРТ",
+  "preview.offset_leds": "Смещение: {count} LED",
+  "preview.direction.cw": "По часовой",
+  "preview.direction.ccw": "Против часовой",
+  "preview.edge.top": "Верх",
+  "preview.edge.right": "Право",
+  "preview.edge.bottom": "Низ",
+  "preview.edge.left": "Лево",
+  "preview.no_calibration": "Нет данных калибровки. Сначала откалибруйте устройство.",
   "server.healthy": "Сервер онлайн",
   "server.offline": "Сервер офлайн",
   "error.unauthorized": "Не авторизован - пожалуйста, войдите",