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/css/modal.css

@@ -269,6 +269,8 @@
     font-size: 0.9em;
 }
 
+/* FPS chart for api_input test preview — reuses .target-fps-row from cards.css */
+
 /* Composite layers preview */
 .css-test-layers {
     display: flex;
@@ -346,7 +348,107 @@
     opacity: 1;
 }
 
-/* ── Log viewer ─────────────────────────────────────────────── */
+/* ── Settings modal tabs ───────────────────────────────────── */
+
+.settings-tab-bar {
+    display: flex;
+    gap: 0;
+    border-bottom: 2px solid var(--border-color);
+    padding: 0 1.25rem;
+}
+
+.settings-tab-btn {
+    background: none;
+    border: none;
+    padding: 8px 16px;
+    font-size: 0.9rem;
+    font-weight: 500;
+    color: var(--text-secondary);
+    cursor: pointer;
+    border-bottom: 2px solid transparent;
+    margin-bottom: -2px;
+    transition: color 0.2s ease, border-color 0.25s ease;
+}
+
+.settings-tab-btn:hover {
+    color: var(--text-color);
+}
+
+.settings-tab-btn.active {
+    color: var(--primary-text-color);
+    border-bottom-color: var(--primary-color);
+}
+
+.settings-panel {
+    display: none;
+}
+
+.settings-panel.active {
+    display: block;
+    animation: tabFadeIn 0.25s ease-out;
+}
+
+/* ── Log viewer overlay (full-screen) ──────────────────────── */
+
+.log-overlay {
+    position: fixed;
+    inset: 0;
+    z-index: 2100;
+    display: flex;
+    flex-direction: column;
+    background: var(--bg-color, #111);
+    padding: 12px 16px;
+    animation: fadeIn 0.2s ease-out;
+}
+
+.log-overlay-close {
+    position: absolute;
+    top: 8px;
+    right: 12px;
+    background: none;
+    border: none;
+    color: var(--text-secondary);
+    font-size: 1.3rem;
+    cursor: pointer;
+    width: 32px;
+    height: 32px;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    border-radius: 6px;
+    z-index: 1;
+    transition: color 0.15s, background 0.15s;
+}
+
+.log-overlay-close:hover {
+    color: var(--text-color);
+    background: var(--border-color);
+}
+
+.log-overlay-toolbar {
+    display: flex;
+    align-items: center;
+    gap: 8px;
+    padding-bottom: 10px;
+    padding-right: 36px;           /* space for corner close btn */
+    flex-shrink: 0;
+}
+
+.log-overlay-toolbar h3 {
+    margin: 0;
+    font-size: 1rem;
+    white-space: nowrap;
+    margin-right: 4px;
+}
+
+.log-overlay .log-viewer-output {
+    flex: 1;
+    max-height: none;
+    border-radius: 8px;
+    min-height: 0;
+}
+
+/* ── Log viewer base ───────────────────────────────────────── */
 
 .log-viewer-output {
     background: #0d0d0d;