Restaurant mode Phase 2: menu depth — categories, stations, modifiers, courses

Builds on Phase 1 with the menu structure restaurants need:
- Menu setup page (restaurant mode): categories, kitchen stations, and modifier
  groups with options (price deltas).
- Products gain category, kitchen station, default course, and attached modifier
  groups (managed on the product form).
- Ordering: the ticket groups the catalog by category and, when a product has
  modifier groups, opens a picker (respects min/max select) for options + notes +
  course before adding. Effective price = base + modifier deltas (resolved
  server-side; client prices are never trusted).
- Fire-by-course: send the whole tab or just one course to the kitchen.
- KDS: filter by station; each item shows its station, course, modifiers and notes.

Schema additive (pos_categories, pos_stations, pos_modifier_groups, pos_modifiers,
product↔group pivot, pos_sale_line_modifiers; category/station/course columns on
products and lines). PosRestaurantTest covers modifiers, course and station routing;
suite green (11 passed).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/Models/PosSaleLine.php

@@ -20,9 +20,18 @@ class PosSaleLine extends Model
     /** States the KDS bump button cycles through, in order. */
     public const KITCHEN_FLOW = [self::KITCHEN_QUEUED, self::KITCHEN_PREPARING, self::KITCHEN_READY, self::KITCHEN_SERVED];
 
+    /** Ordered courses for fire-by-course (key => label). */
+    public const COURSES = [
+        'starter' => 'Starter',
+        'main' => 'Main',
+        'dessert' => 'Dessert',
+        'drink' => 'Drink',
+    ];
+
     protected $fillable = [
         'pos_sale_id',
         'product_id',
+        'station_id',
         'name',
         'unit_price_minor',
         'quantity',
@@ -30,6 +39,7 @@ class PosSaleLine extends Model
         'position',
         'kitchen_state',
         'notes',
+        'course',
     ];
 
     protected function casts(): array
@@ -51,4 +61,14 @@ class PosSaleLine extends Model
     {
         return $this->belongsTo(PosProduct::class, 'product_id');
     }
+
+    public function station(): BelongsTo
+    {
+        return $this->belongsTo(PosStation::class, 'station_id');
+    }
+
+    public function modifiers(): \Illuminate\Database\Eloquent\Relations\HasMany
+    {
+        return $this->hasMany(PosSaleLineModifier::class, 'pos_sale_line_id');
+    }
 }