Restructure batch origins: nested entries per ingredient with Supplier/Farmer selects

Each BatchOrigin (spice) now has multiple BatchOriginEntry rows, replacing the flat
single-supplier/farmer fields. Lieferant and Landwirt are Select fields backed by
dedicated tables with inline create support. Migration preserves existing data.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/Models/BatchOrigin.php

@@ -6,7 +6,7 @@ use Illuminate\Database\Eloquent\Model;
 
 class BatchOrigin extends Model
 {
-    protected $fillable = ['batch_id', 'spice_id', 'supplier_id', 'origin_country', 'farmer', 'notes'];
+    protected $fillable = ['batch_id', 'spice_id'];
 
     public function batch()
     {
@@ -18,8 +18,8 @@ class BatchOrigin extends Model
         return $this->belongsTo(Spice::class);
     }
 
-    public function supplier()
+    public function entries()
     {
-        return $this->belongsTo(Supplier::class);
+        return $this->hasMany(BatchOriginEntry::class);
     }
 }