Add LED skip start/end, rename standby_interval to keepalive_interval, remove migrations

LED skip: set first N and last M LEDs to black on a target. Color sources
(static, gradient, effect, color cycle) render across only the active
(non-skipped) LEDs. Processor pads with blacks before sending to device.

Rename standby_interval → keepalive_interval across all Python, API
schemas, and JS. from_dict falls back to old key for existing configs.

Remove legacy migration functions (_migrate_devices_to_targets,
_migrate_targets_to_color_strips) and legacy fields from target model.

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

server/src/wled_controller/static/css/modal.css

@@ -211,6 +211,26 @@
     font-style: italic;
 }
 
+.inline-fields {
+    display: flex;
+    gap: 12px;
+}
+
+.inline-field {
+    flex: 1;
+}
+
+.inline-field label {
+    display: block;
+    margin-bottom: 4px;
+    font-size: 0.85rem;
+    color: #aaa;
+}
+
+.inline-field input[type="number"] {
+    width: 100%;
+}
+
 .fps-hint {
     display: block;
     margin-top: 4px;

server/src/wled_controller/static/js/features/targets.js

@@ -85,7 +85,9 @@ class TargetEditorModal extends Modal {
             device: document.getElementById('target-editor-device').value,
             css: document.getElementById('target-editor-css').value,
             fps: document.getElementById('target-editor-fps').value,
-            standby_interval: document.getElementById('target-editor-keepalive-interval').value,
+            keepalive_interval: document.getElementById('target-editor-keepalive-interval').value,
+            led_skip_start: document.getElementById('target-editor-skip-start').value,
+            led_skip_end: document.getElementById('target-editor-skip-end').value,
         };
     }
 }
@@ -179,8 +181,10 @@ export async function showTargetEditor(targetId = null) {
             const fps = target.fps ?? 30;
             document.getElementById('target-editor-fps').value = fps;
             document.getElementById('target-editor-fps-value').textContent = fps;
-            document.getElementById('target-editor-keepalive-interval').value = target.standby_interval ?? 1.0;
-            document.getElementById('target-editor-keepalive-interval-value').textContent = target.standby_interval ?? 1.0;
+            document.getElementById('target-editor-keepalive-interval').value = target.keepalive_interval ?? 1.0;
+            document.getElementById('target-editor-keepalive-interval-value').textContent = target.keepalive_interval ?? 1.0;
+            document.getElementById('target-editor-skip-start').value = target.led_skip_start ?? 0;
+            document.getElementById('target-editor-skip-end').value = target.led_skip_end ?? 0;
             document.getElementById('target-editor-title').textContent = t('targets.edit');
         } else {
             // Creating new target — first option is selected by default
@@ -190,6 +194,8 @@ export async function showTargetEditor(targetId = null) {
             document.getElementById('target-editor-fps-value').textContent = '30';
             document.getElementById('target-editor-keepalive-interval').value = 1.0;
             document.getElementById('target-editor-keepalive-interval-value').textContent = '1.0';
+            document.getElementById('target-editor-skip-start').value = 0;
+            document.getElementById('target-editor-skip-end').value = 0;
             document.getElementById('target-editor-title').textContent = t('targets.add');
         }
 
@@ -233,6 +239,8 @@ export async function saveTargetEditor() {
     const deviceId = document.getElementById('target-editor-device').value;
     const cssId = document.getElementById('target-editor-css').value;
     const standbyInterval = parseFloat(document.getElementById('target-editor-keepalive-interval').value);
+    const ledSkipStart = parseInt(document.getElementById('target-editor-skip-start').value) || 0;
+    const ledSkipEnd = parseInt(document.getElementById('target-editor-skip-end').value) || 0;
 
     if (!name) {
         targetEditorModal.showError(t('targets.error.name_required'));
@@ -246,7 +254,9 @@ export async function saveTargetEditor() {
         device_id: deviceId,
         color_strip_source_id: cssId,
         fps,
-        standby_interval: standbyInterval,
+        keepalive_interval: standbyInterval,
+        led_skip_start: ledSkipStart,
+        led_skip_end: ledSkipEnd,
     };
 
     try {

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

@@ -373,6 +373,10 @@
   "targets.interpolation.dominant": "Dominant",
   "targets.smoothing": "Smoothing:",
   "targets.smoothing.hint": "Temporal blending between frames (0=none, 1=full). Reduces flicker.",
+  "targets.led_skip": "LED Skip:",
+  "targets.led_skip.hint": "Number of LEDs at the start and end of the strip to keep black. Color sources will render only across the active (non-skipped) LEDs.",
+  "targets.led_skip_start": "Start:",
+  "targets.led_skip_end": "End:",
   "targets.keepalive_interval": "Keep Alive Interval:",
   "targets.keepalive_interval.hint": "How often to resend the last frame when the source is static, keeping the device in live mode (0.5-5.0s)",
   "targets.created": "Target created successfully",

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

@@ -373,6 +373,10 @@
   "targets.interpolation.dominant": "Доминантный",
   "targets.smoothing": "Сглаживание:",
   "targets.smoothing.hint": "Временное смешивание между кадрами (0=нет, 1=полное). Уменьшает мерцание.",
+  "targets.led_skip": "Пропуск LED:",
+  "targets.led_skip.hint": "Количество светодиодов в начале и конце ленты, которые остаются чёрными. Источники цвета будут рендериться только на активных (непропущенных) LED.",
+  "targets.led_skip_start": "Начало:",
+  "targets.led_skip_end": "Конец:",
   "targets.keepalive_interval": "Интервал поддержания связи:",
   "targets.keepalive_interval.hint": "Как часто повторно отправлять последний кадр при статичном источнике для удержания устройства в режиме live (0.5-5.0с)",
   "targets.created": "Цель успешно создана",