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/Models/Central/Subscription.php

@@ -0,0 +1,64 @@
+<?php
+
+namespace App\Models\Central;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class Subscription extends Model
+{
+    public const STATUSES = [
+        'pending' => 'În așteptare',
+        'paid' => 'Plătit',
+        'overdue' => 'Depășit termen',
+        'cancelled' => 'Anulat',
+        'refunded' => 'Refundat',
+    ];
+
+    public const PERIODS = [
+        'monthly' => 'Lunar',
+        'yearly' => 'Anual',
+    ];
+
+    public const PAYMENT_METHODS = [
+        'card' => 'Card',
+        'bank_transfer' => 'Transfer bancar',
+        'cash' => 'Numerar',
+        'other' => 'Altă metodă',
+    ];
+
+    protected $fillable = [
+        'company_id', 'plan_id',
+        'period', 'amount', 'currency', 'status',
+        'period_start', 'period_end', 'paid_at', 'due_at',
+        'invoice_number', 'payment_method', 'reference', 'notes',
+    ];
+
+    protected $casts = [
+        'amount' => 'decimal:2',
+        'period_start' => 'date',
+        'period_end' => 'date',
+        'paid_at' => 'datetime',
+        'due_at' => 'datetime',
+    ];
+
+    public function company(): BelongsTo
+    {
+        return $this->belongsTo(Company::class);
+    }
+
+    public function plan(): BelongsTo
+    {
+        return $this->belongsTo(Plan::class);
+    }
+
+    public static function generateInvoiceNumber(): string
+    {
+        return sprintf('INV-%s-%04d',
+            date('Ym'),
+            (static::whereYear('created_at', date('Y'))
+                ->whereMonth('created_at', date('m'))
+                ->count()) + 1
+        );
+    }
+}