Add printer cost (€0.35/h) to price estimation

Adds depreciation/electricity as a separate line item in the production
cost breakdown. Included in the markup base so it contributes to margin.
Configurable via PRINTER_COST_PER_HOUR env var (default 0.35).
Bracket gross total updates automatically.

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

app/templates/job_detail.html

@@ -155,6 +155,7 @@
       {{ (estimation.material_factor * 100) | round | int }}% material factor
       · {{ estimation.print_speed | int }} g/h
       · {{ estimation.price_per_kg }} €/kg
+      · {{ estimation.printer_cost_per_hour }} €/h printer
       · {{ estimation.vat_rate }}% VAT
     </span>
   </div>
@@ -188,6 +189,8 @@
                 <td class="border-0">{{ "%.2f"|format(estimation.filament_cost) }} €</td></tr>
             <tr><td class="text-secondary">+ 20 % misprint</td>
                 <td>{{ "%.2f"|format(estimation.filament_cost * 1.2) }} €</td></tr>
+            <tr><td class="text-secondary">Printer ({{ estimation.printer_cost_per_hour }} €/h)</td>
+                <td>{{ "%.2f"|format(estimation.printer_cost) }} €</td></tr>
           </tbody>
         </table>
       </div>