Unify process picker, improve notification CSS editor, remove notification led_count

- Extract shared process picker module (core/process-picker.js) used by
  both automation conditions and notification CSS app filter
- Remove led_count property from notification CSS source (backend + frontend)
- Replace comma-separated app filter with newline-separated textarea + browse
- Inline color cycle add button (+) into the color row
- Fix notification app color layout to horizontal rows

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

server/src/wled_controller/static/css/modal.css

@@ -912,6 +912,48 @@
     line-height: 1;
 }
 
+.color-cycle-add-btn {
+    width: 36px;
+    height: 28px;
+    min-width: unset;
+    padding: 0;
+    font-size: 1.1rem;
+    line-height: 1;
+}
+
+/* ── Notification app color mappings ─────────────────────────── */
+
+.notif-app-color-row {
+    display: flex;
+    align-items: center;
+    gap: 6px;
+    margin-bottom: 4px;
+}
+
+.notif-app-color-row .notif-app-name {
+    flex: 1;
+    min-width: 0;
+}
+
+.notif-app-color-row .notif-app-color {
+    width: 36px;
+    height: 32px;
+    border: 1px solid var(--border-color);
+    border-radius: 4px;
+    padding: 1px;
+    cursor: pointer;
+    background: transparent;
+    flex-shrink: 0;
+}
+
+.notif-app-color-remove {
+    font-size: 0.7rem;
+    padding: 0 4px;
+    min-width: unset;
+    height: 32px;
+    line-height: 1;
+}
+
 /* ── Composite layer editor ────────────────────────────────────── */
 
 #composite-layers-list {