feat: new value source types (HA entity, gradient map, strip extract) + UI fixes

New value source types:
- ha_entity: reads numeric values from HA entity state/attribute, normalizes
  via min/max range, applies EMA smoothing. EntitySelect for HA connection
  and entity selection with live entity list fetching.
- gradient_map: maps a float value source (0-1) through a gradient entity.
  EntitySelect for both input source and gradient with inline previews.
- css_extract: extracts single color by averaging LED range from a color
  strip source. EntitySelect for source selection.

Value source type picker:
- Filter tabs (All / Numeric / Color) above the icon grid
- showTypePicker extended with filterTabs + onFilterChange support

Palette selectors converted to EntitySelect:
- Effect palette, gradient preset, and audio palette selectors now use
  command-palette style EntitySelect with gradient strip previews

Tab indicator fixes:
- Icon now updates on tab switch (was passing no args to updateTabIndicator)
- Visible with any background effect active, not just Noise Field
- Noise Field is the default background effect for new users

Dashboard section collapse fix:
- Split header into clickable toggle (chevron+label) and non-clickable
  actions area — buttons no longer trigger collapse/expand

Discriminated union fix (422 errors):
- source_type/target_type now always included in update payloads for:
  CSS editor, LED target, HA light target, simple calibration,
  advanced calibration

server/src/wled_controller/static/css/components.css

@@ -845,6 +845,32 @@ textarea:focus-visible {
     pointer-events: none;
 }
 
+.type-picker-tabs {
+    display: flex;
+    gap: 4px;
+    margin-bottom: 8px;
+}
+.type-picker-tab {
+    flex: 1;
+    padding: 6px 12px;
+    border: 1px solid var(--border-color, #333);
+    border-radius: 6px;
+    background: var(--surface-2, #1e1e2e);
+    color: var(--text-secondary, #999);
+    font-size: 0.8rem;
+    cursor: pointer;
+    transition: background 0.15s, color 0.15s, border-color 0.15s;
+}
+.type-picker-tab:hover {
+    background: var(--surface-3, #2a2a3e);
+    color: var(--text-primary, #e0e0e0);
+}
+.type-picker-tab.active {
+    background: var(--primary-color, #63b3ed);
+    color: #fff;
+    border-color: var(--primary-color, #63b3ed);
+}
+
 /* ── Entity Palette (command-palette style selector) ─────── */
 
 .entity-palette-overlay {