Rework API input CSS: segments, remove led_count, HAOS light, test preview

API Input CSS rework:
- Remove led_count field from ApiInputColorStripSource (always auto-sizes)
- Add segment-based payload: solid, per_pixel, gradient modes
- Segments applied in order (last wins on overlap), auto-grow buffer
- Backward compatible: legacy {"colors": [...]} still works
- Pydantic validation: mode-specific field requirements

Test preview:
- Enable test preview button on api_input cards
- Hide LED/FPS controls for api_input (sender controls those)
- Show input source selector for all CSS tests (preselected)
- FPS sparkline chart using shared createFpsSparkline (same as target cards)
- Server only sends frames when push_generation changes (no idle frames)

HAOS integration:
- New light.py: ApiInputLight entity per api_input source (RGB + brightness)
- turn_on pushes solid segment, turn_off pushes fallback color
- Register wled_screen_controller.set_leds service for arbitrary segments
- New services.yaml with field definitions
- Coordinator: push_colors() and push_segments() methods
- Platform.LIGHT added to platforms list

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

custom_components/wled_screen_controller/__init__.py

@@ -4,6 +4,8 @@ from __future__ import annotations
 import logging
 from datetime import timedelta
 
+import voluptuous as vol
+
 from homeassistant.config_entries import ConfigEntry
 from homeassistant.const import Platform
 from homeassistant.core import HomeAssistant
@@ -29,6 +31,7 @@ _LOGGER = logging.getLogger(__name__)
 
 PLATFORMS: list[Platform] = [
     Platform.BUTTON,
+    Platform.LIGHT,
     Platform.SWITCH,
     Platform.SENSOR,
     Platform.NUMBER,
@@ -148,6 +151,28 @@ async def async_setup_entry(hass: HomeAssistant, entry: ConfigEntry) -> bool:
 
     coordinator.async_add_listener(_on_coordinator_update)
 
+    # Register set_leds service (once across all entries)
+    async def handle_set_leds(call) -> None:
+        """Handle the set_leds service call."""
+        source_id = call.data["source_id"]
+        segments = call.data["segments"]
+        for entry_data in hass.data[DOMAIN].values():
+            coord = entry_data.get(DATA_COORDINATOR)
+            if coord:
+                await coord.push_segments(source_id, segments)
+                break
+
+    if not hass.services.has_service(DOMAIN, "set_leds"):
+        hass.services.async_register(
+            DOMAIN,
+            "set_leds",
+            handle_set_leds,
+            schema=vol.Schema({
+                vol.Required("source_id"): str,
+                vol.Required("segments"): list,
+            }),
+        )
+
     await hass.config_entries.async_forward_entry_setups(entry, PLATFORMS)
 
     return True