feat(timetable): factories + ArtistTimetableDevSeeder

Eight factories with named states (Genre, Artist, ArtistContact, Stage,
ArtistEngagement, Performance, AdvanceSection, AdvanceSubmission).

ArtistTimetableDevSeeder hooked into DevSeeder::seedEchtFeesten after
the form-builder showcase. Produces:
- 4 stages (Mainstage, Havana, Stairway, Socialite) with prototype-style
  hex colours
- 4 stages × 3 sub-events = 12 stage_days rows
- 4 genres (Hardstyle, Techno, Indie, Live band)
- 6 master artists, each with one tour-manager ArtistContact
- 12 engagements with status mix (1 Draft, 2 Requested, 3 Option,
  2 Confirmed, 3 Contracted, 1 Cancelled). Two artists have two
  engagements each (different sub-events) — exercises D17 multi-
  engagement-per-artist.
- 13 performances, including one parked (stage_id=null = wachtrij)
  and one B2B pair within 3 minutes on Mainstage Saturday to seed
  the Session 4 frontend B2B detector.

Also fix LogOptions method name across 8 models: dontSubmitEmptyLogs()
→ dontLogEmptyChanges() (Spatie's actual API; surfaced when DevSeeder
ran).

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

api/app/Models/Performance.php

@@ -56,7 +56,7 @@ final class Performance extends Model
     {
         return LogOptions::defaults()
             ->logFillable()
-            ->dontSubmitEmptyLogs();
+            ->dontLogEmptyChanges();
     }
 
     public function engagement(): BelongsTo