Replace bare — and generic None in selectors with descriptive None (reason) labels

All optional entity selectors now use the format "None (description)" with
i18n keys instead of hardcoded "—" or bare "None". Added common.none_no_cspt,
common.none_no_input, common.none_own_speed keys to all 3 locales. Updated
frontend context with the convention.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -410,6 +410,9 @@
   "common.edit": "Edit",
   "common.clone": "Clone",
   "common.none": "None",
+  "common.none_no_cspt": "None (no processing template)",
+  "common.none_no_input": "None (no input source)",
+  "common.none_own_speed": "None (use own speed)",
   "palette.search": "Search…",
   "section.filter.placeholder": "Filter...",
   "section.filter.reset": "Clear filter",
@@ -803,7 +806,7 @@
   "automations.scene": "Scene:",
   "automations.scene.hint": "Scene preset to activate when conditions are met",
   "automations.scene.search_placeholder": "Search scenes...",
-  "automations.scene.none_selected": "No scene",
+  "automations.scene.none_selected": "None (no scene)",
   "automations.scene.none_available": "No scenes available",
   "automations.deactivation_mode": "Deactivation:",
   "automations.deactivation_mode.hint": "What happens when conditions stop matching",
@@ -1097,7 +1100,7 @@
   "color_strip.composite.blend_mode.screen.desc": "Brightens, inverse of multiply",
   "color_strip.composite.opacity": "Opacity",
   "color_strip.composite.brightness": "Brightness",
-  "color_strip.composite.brightness.none": "— None —",
+  "color_strip.composite.brightness.none": "None (full brightness)",
   "color_strip.composite.processing": "Processing",
   "color_strip.composite.enabled": "Enabled",
   "color_strip.composite.error.min_layers": "At least 1 layer is required",