Central panel SaaS upgrade — Plans/Subscriptions/SuperAdmins/Detail page

Models & migrations:
- subscriptions table (company, plan, period, amount, status, dates, invoice)
- super_admins: role enum (owner/admin/support/sales/finance) + phone + notes
- Subscription model with STATUSES/PERIODS/PAYMENT_METHODS + invoice number
  generator + extends company.active_until on mark_paid
- Company model: subscriptions() + latestSubscription() relations
- SuperAdmin model: role helpers (isOwner, canManageBilling, canManageTenants)

Filament Central panel:
- PlanResource (CRUD, features checklist, limits per plan, abonati count badge)
- SubscriptionResource (CRUD, mark_paid action, navigation badge for overdue)
- SuperAdminResource (CRUD, reset password, toggle 2FA, can't self-delete)
- ViewCompany page with live stats (users/clients/vehicles/WO/parts/revenue/
  storage/last_login + days_until_expiry), subscriptions history table,
  config snapshot, action buttons (open/issue invoice/upload logo/suspend)
- CompanyResource: row click → view, openUrlInNewTab action, recordTitleAttribute,
  empty state, view route registered
- PlatformStats widget upgraded: 6 cards (incl. MRR realized this month, overdue
  invoices count, click-through to filtered tables)
- RevenueChart: 12-month MRR line chart
- RecentTenants: latest 8 tenants with click-through
- PendingPayments: pending+overdue invoices table
- Database notifications enabled + Cmd+K global search
- HEAD_END render hook: PWA manifest + theme color + emoji favicon
- /admin-manifest.json route

Seeder:
- Plans aligned with new FEATURE_OPTIONS (kanban/pdf/reports/ai/api/reverb/etc)
- 4 plans: Free / Basic / Pro / Enterprise (with proper limits)
- SuperAdmin gets role='owner'
- Demo subscription for psauto on Pro plan, marked paid this month

app/Filament/Central/Widgets/RevenueChart.php

@@ -0,0 +1,48 @@
+<?php
+
+namespace App\Filament\Central\Widgets;
+
+use App\Models\Central\Subscription;
+use Filament\Widgets\ChartWidget;
+
+class RevenueChart extends ChartWidget
+{
+    protected ?string $heading = 'Venit lunar (MRR)';
+
+    protected static ?int $sort = 2;
+
+    protected int|string|array $columnSpan = 'full';
+
+    protected ?string $pollingInterval = null;
+
+    protected function getData(): array
+    {
+        $months = collect(range(11, 0))->map(fn ($n) => now()->subMonths($n));
+
+        $values = $months->map(function ($m) {
+            return (float) Subscription::where('status', 'paid')
+                ->whereYear('paid_at', $m->year)
+                ->whereMonth('paid_at', $m->month)
+                ->sum('amount');
+        });
+
+        return [
+            'datasets' => [
+                [
+                    'label' => 'MRR (MDL)',
+                    'data' => $values->toArray(),
+                    'backgroundColor' => 'rgba(34, 197, 94, 0.15)',
+                    'borderColor' => '#22c55e',
+                    'tension' => 0.35,
+                    'fill' => true,
+                ],
+            ],
+            'labels' => $months->map(fn ($m) => $m->format('M Y'))->toArray(),
+        ];
+    }
+
+    protected function getType(): string
+    {
+        return 'line';
+    }
+}