feat: Add company association to projects with role management

- Created Company model and migration with fields: name, tax_id, address, phone, email, website, type, notes
- Created company_project pivot table with role_in_project field
- Added relationships: Project.companies() and Company.projects()
- Created Livewire component ProjectCompanies for managing company assignments
- Added 'Companies' tab to project edit interface alongside Phases and Users tabs
- Implemented assign/remove company functionality with role selection
- Applied same permissions logic as user assignment (assign users permission or Admin role)

app/Models/Project.php

@@ -34,6 +34,13 @@ class Project extends Model
         return $this->belongsToMany(User::class)->withPivot('role_in_project');
     }
 
+    public function companies()
+    {
+        return $this->belongsToMany(Company::class, 'company_project')
+                    ->withPivot('role_in_project')
+                    ->withTimestamps();
+    }
+
     public function creator()
     {
         return $this->belongsTo(User::class, 'created_by');