[Feature] Many-to-Many Relationship Support

[devalade]

Description

Currently belongsToMany relationships are added to the model, but migration pivot tables and attach/detach UI are missing.

Current Behavior

php artisan crudify:generate Post \
  --relationships="tags:belongsToMany:Tag"

Only generates model method - no pivot table, no UI for attaching tags.

Expected Behavior

• Generate pivot table migration (post_tag)
• Generate Tag model if it doesn't exist
• Livewire Create/Edit: Add multi-select checkbox/tag input for attaching
• Index: Show related tags as badges
• Form request: Validate array of IDs with Rule::exists

Example UI

<div class="space-y-2">
    <label>Tags</label>
    <div class="flex flex-wrap gap-2">
        @foreach($allTags as $tag)
            <label class="inline-flex items-center">
                <input type="checkbox" wire:model="selectedTags" value="{{ $tag->id }}">
                <span>{{ $tag->name }}</span>
            </label>
        @endforeach
    </div>
</div>

API

$post->tags()->sync($this->selectedTags);