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>

server/src/wled_controller/static/js/features/sync-clocks.js

@@ -98,6 +98,7 @@ export async function saveSyncClock() {
         }
         showToast(t(id ? 'sync_clock.updated' : 'sync_clock.created'), 'success');
         syncClockModal.forceClose();
+        syncClocksCache.invalidate();
         await loadPictureSources();
     } catch (e) {
         if (e.isAuth) return;
@@ -143,6 +144,7 @@ export async function deleteSyncClock(clockId) {
             throw new Error(err.detail || `HTTP ${resp.status}`);
         }
         showToast(t('sync_clock.deleted'), 'success');
+        syncClocksCache.invalidate();
         await loadPictureSources();
     } catch (e) {
         if (e.isAuth) return;