CSS: add StaticColorStripSource type with auto-sized LED count

Introduces a new 'static' source type that fills all device LEDs with a
single constant RGB color — no screen capture or processing required.

- StaticColorStripSource storage model (color + led_count=0 auto-size)
- StaticColorStripStream: no background thread, configure() sizes to device
  LED count at processor start; hot-updates preserve runtime size
- ColorStripStreamManager dispatches static sources (no LiveStream needed)
- WledTargetProcessor calls stream.configure(device_led_count) on start
- API schemas/routes: source_type Literal["picture","static"]; color field;
  overlay/calibration-test endpoints return 400 for static
- Frontend: type selector modal, color picker, type-aware card rendering
  (🎨 icon + color swatch), LED count field hidden for static type
- Locale keys: color_strip.type, color_strip.static_color (en + ru)

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

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

@@ -563,11 +563,17 @@
   "color_strip.test_device.hint": "Select a device to send test pixels to when clicking edge toggles",
   "color_strip.leds": "LED count",
   "color_strip.led_count": "LED Count:",
-  "color_strip.led_count.hint": "Total number of LEDs on the physical strip. Set to 0 to use the sum from calibration. Useful when the strip has LEDs behind the TV that are not mapped to screen edges — those LEDs will be sent black.",
+  "color_strip.led_count.hint": "Total number of LEDs on the physical strip. For screen sources: 0 = auto from calibration (extra LEDs not mapped to edges will be black). For static color: set to match your device LED count.",
   "color_strip.created": "Color strip source created",
   "color_strip.updated": "Color strip source updated",
   "color_strip.deleted": "Color strip source deleted",
   "color_strip.delete.confirm": "Are you sure you want to delete this color strip source?",
   "color_strip.delete.referenced": "Cannot delete: this source is in use by a target",
-  "color_strip.error.name_required": "Please enter a name"
+  "color_strip.error.name_required": "Please enter a name",
+  "color_strip.type": "Type:",
+  "color_strip.type.hint": "Picture Source derives LED colors from a screen capture. Static Color fills all LEDs with a single constant color.",
+  "color_strip.type.picture": "Picture Source",
+  "color_strip.type.static": "Static Color",
+  "color_strip.static_color": "Color:",
+  "color_strip.static_color.hint": "The solid color that will be sent to all LEDs on the strip."
 }