feat(configurator): server-side surface area calculation from STL

Add trimesh-based surface area calculation for uploaded STL files:
- New /fp/configurator/calculate_surface_area jsonrpc endpoint
- action_calculate_surface_area() method on fp.part.catalog
- "Calculate from 3D Model" button visible when a 3D model is attached
- Returns area in sq in (converted from mm2), vertex/face counts,
  and bounding box dimensions

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

fusion-plating/fusion_plating_configurator/controllers/configurator_controller.py

@@ -0,0 +1,52 @@
+# -*- coding: utf-8 -*-
+# Copyright 2026 Nexa Systems Inc.
+# License OPL-1 (Odoo Proprietary License v1.0)
+# Part of the Fusion Plating product family.
+
+import base64
+import io
+import logging
+
+from odoo import http
+from odoo.http import request
+
+_logger = logging.getLogger(__name__)
+
+
+class FpConfiguratorController(http.Controller):
+
+    @http.route('/fp/configurator/calculate_surface_area', type='jsonrpc', auth='user')
+    def calculate_surface_area(self, attachment_id, **kw):
+        """Calculate surface area from an uploaded STL file using trimesh."""
+        attachment = request.env['ir.attachment'].browse(int(attachment_id))
+        if not attachment.exists():
+            return {'error': 'Attachment not found.'}
+
+        try:
+            import trimesh
+        except ImportError:
+            return {'error': 'trimesh library not installed. Run: pip install trimesh'}
+
+        try:
+            raw = base64.b64decode(attachment.datas)
+            mesh = trimesh.load(io.BytesIO(raw), file_type='stl')
+
+            # trimesh returns area in the file's native units (usually mm²)
+            area_mm2 = mesh.area
+            area_sqin = area_mm2 / 645.16  # mm² to sq in
+
+            return {
+                'surface_area': round(area_sqin, 4),
+                'surface_area_mm2': round(area_mm2, 2),
+                'unit': 'sq_in',
+                'vertex_count': len(mesh.vertices),
+                'face_count': len(mesh.faces),
+                'bounding_box': {
+                    'x': round(float(mesh.bounding_box.extents[0]), 2),
+                    'y': round(float(mesh.bounding_box.extents[1]), 2),
+                    'z': round(float(mesh.bounding_box.extents[2]), 2),
+                },
+            }
+        except Exception as e:
+            _logger.warning('STL surface area calculation failed: %s', e)
+            return {'error': str(e)}