feat(frontend): add drag-and-drop reordering and inline editing for routine steps

- Install svelte-dnd-action v0.9.69
- Use dragHandleZone + dragHandle for per-step ⋮⋮ drag handles
- PATCH only steps whose order_index changed after a drop
- Inline edit mode (✎ button) expands step in-place: product steps show product/dose/region selects; action steps show action_type/notes
- DnD disabled while a step is being edited

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

frontend/package.json

@@ -31,6 +31,7 @@
 		"clsx": "^2.1.1",
 		"lucide-svelte": "^0.575.0",
 		"mode-watcher": "^1.1.0",
+		"svelte-dnd-action": "^0.9.69",
 		"tailwind-merge": "^3.5.0"
 	}
 }