fix(plating): CoC signer follows Settings "Certificate Owner" (no stale freeze)

Changing Settings -> Certificate Owner didn't move existing certs: the signer
was snapshotted from the company owner at cert-creation time, and the CoC
prefers that snapshot over the live owner.

- _fp_create_certificates no longer freezes the company owner into
  certified_by_id; it snapshots ONLY a deliberate per-spec signer. Empty
  certified_by_id then resolves the LIVE company owner in the CoC report.
- action_issue lazy-fill made robust: resolves the company via the SO /
  env.company (fp.certificate has no company_id) so it fills the CURRENT
  owner at issue and the "Certified By" gate still passes.
- Settings help text corrected: signature comes from the user's Plating
  Signature (Preferences -> My Profile), not "HR Employee".
- Data fix on entech: cleared certified_by_id on 5 stale draft CoCs with no
  per-spec signer so they follow the current owner.

Bump certificates 19.0.9.3.0, jobs 19.0.11.4.0. Verified: CoC-30058 resolves
signer = Garry Singh (has Plating Signature), renders clean.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

fusion_plating/fusion_plating_jobs/models/fp_job.py

@@ -2572,8 +2572,10 @@ class FpJob(models.Model):
 
         Resolution sources for the new prefill fields:
           - process_description ← recipe.name (the job's process root)
-          - certified_by_id     ← customer_spec.signer_user_id, falling
-                                  back to company.x_fc_owner_user_id
+          - certified_by_id     ← customer_spec.signer_user_id ONLY
+                                  (a per-spec override). Left empty
+                                  otherwise so the LIVE company owner
+                                  resolves at render / issue time.
           - contact_partner_id  ← partner.x_fc_default_coc_contact_id
           - nc_quantity         ← qty_scrapped + qty_visual_insp_rejects
 
@@ -2596,12 +2598,17 @@ class FpJob(models.Model):
         # sourced from sale_order.x_fc_coating_config_id (since retired);
         # recipe.name is the human-readable replacement.
         recipe = self.recipe_id
-        # Signer resolution: per-spec override wins, company default fills.
+        # Signer resolution (2026-05-28): snapshot ONLY a deliberate
+        # per-spec signer here. Do NOT freeze the company owner into
+        # certified_by_id — leaving it empty lets the CoC report and
+        # action_issue resolve the LIVE company owner (res.company
+        # .x_fc_owner_user_id / Settings "Certificate Owner") at render /
+        # issue time. That way changing the Settings signer flows through
+        # to existing draft certs instead of being frozen to whoever was
+        # the owner when the cert was created.
         signer = False
         if spec and 'signer_user_id' in spec._fields:
             signer = spec.signer_user_id
-        if not signer and 'x_fc_owner_user_id' in self.company_id._fields:
-            signer = self.company_id.x_fc_owner_user_id
         # Contact: per-customer default; blank means manager picks at issue.
         contact = False
         if 'x_fc_default_coc_contact_id' in self.partner_id._fields: