Fix payment amount editable + discount live recalculation

- PaymentsRelationManager: remove broken default() closure on amount;
  use fillForm() on CreateAction instead (correct Filament API) so the
  modal pre-fills with remaining balance (total - paid) but field stays
  fully editable; add minValue/step for numeric UX
- WorkOrderResource: discount_pct is now live(onBlur) with afterStateUpdated
  that recomputes works+parts+subcontract minus discount and sets the
  total field immediately — no Save required to see the effect

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

app/Filament/Tenant/Resources/WorkOrderResource.php

@@ -149,7 +149,20 @@ class WorkOrderResource extends Resource
                 ->columns(3)->collapsible()->collapsed()->compact()
                 ->schema([
                     Forms\Components\Select::make('pay_status')->options(\App\Support\I18n::opts(WorkOrder::PAY_STATUSES))->default('unpaid')->required(),
-                    Forms\Components\TextInput::make('discount_pct')->label(__('Discount %'))->numeric()->default(0),
+                    Forms\Components\TextInput::make('discount_pct')
+                        ->label(__('Discount %'))
+                        ->numeric()
+                        ->default(0)
+                        ->live(onBlur: true)
+                        ->afterStateUpdated(function ($state, callable $set, $record) {
+                            if (! $record) return;
+                            $works = (float) $record->works()->sum('total');
+                            $parts = (float) $record->parts()->sum('total');
+                            $sub   = (float) $record->subcontractJobs()
+                                ->where('status', '!=', 'cancelled')->sum('client_price');
+                            $disc  = min(100, max(0, (float) $state));
+                            $set('total', round(($works + $parts + $sub) * (1 - $disc / 100), 2));
+                        }),
                     Forms\Components\Toggle::make('apply_margin')
                         ->label(__('Aplică marjă internă'))
                         ->default(true)