feat(sub12a+): drop-position simulator in Simple Recipe Editor

Replaces the per-row 'highlight whole row' feedback (operator
couldn't tell whether the new step would land before or after the
hovered row) with a precise insertion-point indicator.

How it works:
- Each row's onDragOver computes ev.clientY vs row midpoint.
  Above midpoint → insertion index = rowIndex (BEFORE).
  Below midpoint → insertion index = rowIndex + 1 (AFTER).
- An <o_fp_drop_indicator> div lives BEFORE the first row and
  AFTER every row. When state.dragOverIndex matches that slot's
  index, the div expands from height:0 to a 2.25rem dashed-green
  reservation strip with a ghost-preview chip ('↓ insert here →
  <icon> <step name>').
- onDragStart captures the dragged step/template's name + icon
  into state.dragPreviewLabel/Icon for the chip text.
- Smooth 80ms height/margin transition so the line glides between
  slots as the cursor moves rather than blinking.
- Trailing dropzone retains its existing 'Drop here to add at end'
  styling. Empty list shows 'Drag a library step here to start'.
- onDrop reads from state.dragOverIndex (set by the most-recent
  onDragOver) so we drop at the simulated position exactly.
- onDragLeave guards against child-element flicker via
  relatedTarget contains() check.
- onDragEnd clears state.dragPreviewLabel/Icon so a half-completed
  drag (cancelled by Esc) doesn't leave the chip stuck on screen.

fusion_plating → 19.0.10.4.0.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

fusion_plating/fusion_plating/__manifest__.py

@@ -5,7 +5,7 @@
 
 {
     'name': 'Fusion Plating',
-    'version': '19.0.10.3.0',
+    'version': '19.0.10.4.0',
     'category': 'Manufacturing/Plating',
     'summary': 'Core plating / metal finishing ERP: facilities, processes, tanks, baths, jobs, operators.',
     'description': """