fix: slug unique check skips soft-deleted + drop DB unique on companies.slug

DB-level unique blocks INSERT even when previous record is soft-deleted.
MariaDB doesn't support partial unique indexes, so we drop the constraint
and rely on Filament validation + provisioner check (whereNull deleted_at).

app/Filament/Central/Resources/CompanyResource.php

@@ -35,7 +35,10 @@ class CompanyResource extends Resource
                         ->required()
                         ->alphaDash()
                         ->maxLength(30)
-                        ->unique(ignoreRecord: true)
+                        ->unique(
+                            ignoreRecord: true,
+                            modifyRuleUsing: fn ($rule) => $rule->whereNull('deleted_at'),
+                        )
                         ->dehydrateStateUsing(fn ($state) => strtolower((string) $state))
                         ->extraInputAttributes(['style' => 'text-transform: lowercase'])
                         ->helperText('Subdomeniul: <slug>.service.mir.md'),