feat(timetable): API resources + LaneResolver helper

Six resources under app/Http/Resources/Api/V1/Artist/ matching
FormSubmissionResource conventions (final class, @mixin model,
optional()->toIso8601String, whenLoaded relationships).

  GenreResource          — id, name, color, sort_order, is_active
  ArtistResource         — master + lifetime/upcoming engagement counts
                           computed lazily from the engagements relation
  ArtistContactResource  — paired with ArtistResource.contacts
  ArtistEngagementResource — full deal block with the RFC D26 Buma/VAT
                           formulas computed live in `computed.*`:
                             buma_amount = fee × buma_pct/100
                                           IFF Organisation handles BUMA
                             vat_grondslag = fee + (buma when Organisation)
                             vat_amount = vat_grondslag × vat_pct/100
                                           when vat_applicable
                             total_cost = fee + buma + vat + Σ breakdown
                           Frontend (Session 5) ports the same formula.
  StageResource          — adds stage_days as a flat array of event_ids
                           (not nested Event resources, to keep payload
                           light)
  PerformanceResource    — `lane` (raw, persisted), `lane_resolved`
                           (computed per D19), `warnings` (overlap +
                           B2B at minimum; capacity-warn refined later)

LaneResolver under app/Services/Artist/ is the pure-logic helper that
PerformanceResource calls. Greedy lowest-non-conflicting lane
assignment over the (stage_id, event_id) cohort sorted by start_at
then by raw lane (so cascade-bumped rows stay where they were
visually). Frontend port lands in Session 4.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

api/app/Http/Resources/Api/V1/Artist/ArtistResource.php

@@ -0,0 +1,69 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Http\Resources\Api\V1\Artist;
+
+use App\Enums\Artist\ArtistEngagementStatus;
+use App\Models\Artist;
+use Illuminate\Http\Request;
+use Illuminate\Http\Resources\Json\JsonResource;
+
+/**
+ * @mixin Artist
+ */
+final class ArtistResource extends JsonResource
+{
+    /**
+     * @return array<string, mixed>
+     */
+    public function toArray(Request $request): array
+    {
+        $lifetime = $this->engagements()
+            ->whereNotIn('booking_status', [
+                ArtistEngagementStatus::Cancelled->value,
+                ArtistEngagementStatus::Rejected->value,
+                ArtistEngagementStatus::Declined->value,
+            ])
+            ->count();
+
+        $upcoming = $this->engagements()
+            ->whereNotIn('booking_status', [
+                ArtistEngagementStatus::Cancelled->value,
+                ArtistEngagementStatus::Rejected->value,
+                ArtistEngagementStatus::Declined->value,
+            ])
+            ->whereHas('event', fn ($q) => $q->where('end_at', '>=', now()))
+            ->count();
+
+        return [
+            'id' => $this->id,
+            'organisation_id' => $this->organisation_id,
+            'name' => $this->name,
+            'slug' => $this->slug,
+            'default_genre_id' => $this->default_genre_id,
+            'default_genre' => GenreResource::make($this->whenLoaded('defaultGenre')),
+            'default_draw' => $this->default_draw,
+            'star_rating' => $this->star_rating,
+            'home_base_country' => $this->home_base_country,
+            'agent_company_id' => $this->agent_company_id,
+            'agent_company' => $this->whenLoaded(
+                'agentCompany',
+                fn () => [
+                    'id' => $this->agentCompany?->id,
+                    'name' => $this->agentCompany?->name,
+                    'handles_buma' => (bool) ($this->agentCompany?->handles_buma ?? false),
+                ],
+            ),
+            'notes' => $this->notes,
+            'contacts' => ArtistContactResource::collection($this->whenLoaded('contacts')),
+            'engagements_summary' => [
+                'lifetime_count' => $lifetime,
+                'upcoming_count' => $upcoming,
+            ],
+            'created_at' => optional($this->created_at)->toIso8601String(),
+            'updated_at' => optional($this->updated_at)->toIso8601String(),
+            'deleted_at' => optional($this->deleted_at)->toIso8601String(),
+        ];
+    }
+}