feat(simple-editor): node_type bug fix + inline library authoring + back nav

Bucket 1 — Generation bug fix
- post-migrate.py for 19.0.18.8.0 promotes flat 'step' children of
  recipes to 'operation' so fp.job._generate_steps() picks them up.
  Filter is narrow: only direct children of node_type='recipe' get
  flipped, tree-editor sub-steps (parent.node_type='operation') are
  untouched. Idempotent. Posts an audit chatter note on each affected
  recipe.
- Simple Editor controller hardcodes node_type='operation' on insert
  + snapshot-import path so future recipes start correct.

Bucket 2 — Inline library authoring
- 6 new JSONRPC routes (/fp/simple_recipe/library/load + save +
  seed_defaults + input/{add,write,remove}, /fp/simple_recipe/tank/list).
- + New Step button in the right pane opens an inline form with name /
  kind / icon / instructions / stations / flags / prompts table.
- Pencil icon on each library row reopens the same form prefilled.
- Step Kind picker leads with 'Generic — no automatic behaviour'.
- 'Seed defaults from kind' calls action_seed_default_inputs server-side
  for kinds that have curated default prompts.

Bucket 3 — Back nav
- '← Recipes' button in the header (or '← Part' when opened from
  Process Composer) mirrors recipe_tree_editor.js, with
  clearBreadcrumbs:true to avoid stack pollution.

Verified on entech: LGPS1104's 19 'step' children now show as
'operation', migration chatter note posted on the recipe, asset cache
busted.

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': '19.0.18.7.4',
+    'version': '19.0.18.8.0',
     'category': 'Manufacturing/Plating',
     'summary': 'Core plating / metal finishing ERP: facilities, processes, tanks, baths, jobs, operators.',
     'description': """