Card bulk operations, remove expand/collapse, graph color picker fix

- Bulk selection mode: Ctrl+Click or toggle button to enter, Escape to exit
- Shift+Click for range select, bottom toolbar with SVG icon action buttons
- All CardSections wired with bulk actions: Delete everywhere,
  Start/Stop for targets, Enable/Disable for automations
- Remove expand/collapse all buttons (no collapsible sections remain)
- Fix graph node color picker overlay persisting after outside click
- Add Icons section to frontend.md conventions
- Add trash2, listChecks, circleOff icons to icon system
- Backend: processing loop performance improvements (monotonic timestamps,
  deque-based FPS tracking)

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

server/src/wled_controller/core/processing/wled_target_processor.py

@@ -595,7 +595,13 @@ class WledTargetProcessor(TargetProcessor):
 
         fps_samples: collections.deque = collections.deque(maxlen=10)
         _fps_sum = 0.0
-        send_timestamps: collections.deque = collections.deque(maxlen=target_fps + 10)
+        send_timestamps: collections.deque = collections.deque(maxlen=self._target_fps + 10)
+
+        def _fps_current_from_timestamps():
+            """Count timestamps within the last second."""
+            cutoff = time.perf_counter() - 1.0
+            return sum(1 for ts in send_timestamps if ts > cutoff)
+
         last_send_time = 0.0
         _last_preview_broadcast = 0.0
         prev_frame_time_stamp = time.perf_counter()
@@ -839,7 +845,7 @@ class WledTargetProcessor(TargetProcessor):
                                 send_timestamps.append(now)
                                 self._metrics.frames_keepalive += 1
                             self._metrics.frames_skipped += 1
-                            self._metrics.fps_current = len(send_timestamps)
+                            self._metrics.fps_current = _fps_current_from_timestamps()
                             await asyncio.sleep(SKIP_REPOLL)
                             continue
 
@@ -864,7 +870,7 @@ class WledTargetProcessor(TargetProcessor):
                                     await self._broadcast_led_preview(send_colors, cur_brightness)
                                     _last_preview_broadcast = now
                             self._metrics.frames_skipped += 1
-                            self._metrics.fps_current = len(send_timestamps)
+                            self._metrics.fps_current = _fps_current_from_timestamps()
                             is_animated = stream.is_animated
                             repoll = SKIP_REPOLL if is_animated else frame_time
                             await asyncio.sleep(repoll)
@@ -923,7 +929,7 @@ class WledTargetProcessor(TargetProcessor):
                         processing_time = now - loop_start
                         self._metrics.fps_potential = 1.0 / processing_time if processing_time > 0 else 0
 
-                        self._metrics.fps_current = len(send_timestamps)
+                        self._metrics.fps_current = _fps_current_from_timestamps()
 
                     except Exception as e:
                         self._metrics.errors_count += 1