Add dynamic brightness value source support for KC targets, fix subtab selector collision

Extend value source brightness modulation to Key Colors targets (matching LED target support).
Also fix stream subtab CSS selector collision that broke target subtab selection, and use 🔢 emoji
for value source UI elements.

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

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

@@ -424,6 +424,9 @@
   "kc.pattern_template": "Pattern Template:",
   "kc.pattern_template.hint": "Select the rectangle pattern to use for color extraction",
   "kc.pattern_template.none": "-- Select a pattern template --",
+  "kc.brightness_vs": "🔢 Brightness Source:",
+  "kc.brightness_vs.hint": "Optional value source that dynamically controls brightness each frame (multiplied with the manual brightness slider)",
+  "kc.brightness_vs.none": "None (manual brightness only)",
   "kc.created": "Key colors target created successfully",
   "kc.updated": "Key colors target updated successfully",
   "kc.deleted": "Key colors target deleted successfully",
@@ -763,7 +766,7 @@
   "audio_source.error.name_required": "Please enter a name",
 
   "streams.group.value": "Value Sources",
-  "value_source.group.title": "🎚️ Value Sources",
+  "value_source.group.title": "🔢 Value Sources",
   "value_source.add": "Add Value Source",
   "value_source.edit": "Edit Value Source",
   "value_source.name": "Name:",
@@ -807,7 +810,7 @@
   "value_source.deleted": "Value source deleted",
   "value_source.delete.confirm": "Are you sure you want to delete this value source?",
   "value_source.error.name_required": "Please enter a name",
-  "targets.brightness_vs": "Brightness Source:",
+  "targets.brightness_vs": "🔢 Brightness Source:",
   "targets.brightness_vs.hint": "Optional value source that dynamically controls brightness each frame (overrides device brightness)",
   "targets.brightness_vs.none": "None (device brightness)"
 }