feat(fusion_repairs): Bundle 6 - M7 failure analytics + M9 margin per repair

M9 margin per repair
- New non-stored computes on repair.order: x_fc_revenue, x_fc_labour_cost,
  x_fc_parts_cost, x_fc_margin, x_fc_margin_pct.
- Revenue: sum of posted out_invoice.amount_untaxed on the repair's sale
  order (handles partial / multi invoice scenarios).
- Labour: sum of (task.duration_hours x technician.x_fc_tech_cost_rate)
  over COMPLETED visits only - avoids counting scheduled-but-not-done time.
- Parts: sum of standard_price x qty for stock moves where
  repair_line_type='add' (parts consumed, not removed).
- New 'Margin' notebook tab on repair.order form, manager-group gated.

M7 failure analytics on the dashboard
- Three new keys in get_dashboard_data():
  * failures_by_product - top 8 products by repair_count in last 90 days
    via _read_group (efficient - no record load)
  * failures_by_symptom - top 8 x_fc_issue_category values
  * margin_summary - revenue/labour/parts/margin/margin_pct + sample_size
    over the same 90-day window
- Three new tiles on the OWL dashboard 'Last 90 Days' section:
  Margin Summary (revenue/labour/parts/margin breakdown),
  Failure Rate by Product, Failure Rate by Symptom.
- New formatMoney + formatPercent helpers on the dashboard JS so values
  display as 'CAD 12,345' rather than raw floats.

Verified end-to-end on local westin-v19:
  Dashboard returned all 9 expected keys.
  Top product: 'M6 X 27 THREADED BARREL' (2 repairs) - actual test data.
  Margin summary over 26 repairs (dev has $0 invoices so values 0.0,
  but the compute path is exercised and shapes are correct).

Bumped to 19.0.1.6.0.

Co-authored-by: Cursor <cursoragent@cursor.com>

fusion_repairs/views/repair_order_views.xml

@@ -114,6 +114,21 @@
                 <page string="AI Brief" name="fusion_ai" invisible="not x_fc_ai_summary">
                     <field name="x_fc_ai_summary" readonly="1"/>
                 </page>
+                <page string="Margin" name="fusion_margin"
+                      groups="fusion_repairs.group_fusion_repairs_manager">
+                    <group>
+                        <group>
+                            <field name="x_fc_revenue" widget="monetary"/>
+                            <field name="x_fc_labour_cost" widget="monetary"/>
+                            <field name="x_fc_parts_cost" widget="monetary"/>
+                        </group>
+                        <group>
+                            <field name="x_fc_margin" widget="monetary"/>
+                            <field name="x_fc_margin_pct" widget="float" digits="[12,1]"/>
+                            <field name="company_currency_id" invisible="1"/>
+                        </group>
+                    </group>
+                </page>
             </xpath>
 
         </field>