Stage 6 — Purchase System: partial receipt + supplier analytics

Schema:
- purchase_items.qty_received (backfilled from `received` boolean)
- purchases.warehouse_id (target warehouse FK)
- supplier_part_prices (price history per supplier/part with purchase ref)
- New status `partial` between ordered and received

Purchase ↔ Warehouse integration:
- Purchase::receiveItem(item, qty, warehouse?) — routes through
  WarehouseService::receive: creates batch + receipt event + supplier price row
- Purchase::receiveAllRemaining(warehouse?) — receives all outstanding lines
- Purchase::recomputeStatus() — auto: ordered → partial → received

Old flat markReceived() removed — every receipt now writes batches + ledger.

Filament:
- Purchase list: progress %, partial badge, warehouse picker on form
- ItemsRelationManager: per-line "Recepționează" with qty + warehouse modal,
  qty_received shown as "X.XX / Y.YY" with colour
- PartResource: new PriceHistoryRelationManager (supplier price history)
- SupplierResource: derived columns onTimeRate / avgDeliveryDays / spend(90d)
  + "Rerating" action

Analytics:
- App\Services\Warehouse\SupplierAnalytics (onTimeRate, avgDeliveryDays,
  spend, count, computedRating)
- `suppliers:rate` artisan command + weekly schedule (Mon 04:00)
- Computed rating: 70% on-time + 20% volume + 10% speed bonus

Tests (6 new, all pass):
- Partial receipt of 3/10 → status=partial + 1 batch + 1 price row
- receiveAllRemaining → status=received with received_at set
- Over-receive throws InvalidArgumentException
- Two partial receipts (4+6) → 2 batches FIFO + status=received
- onTimeRate 50% with 1 on-time + 1 late
- computedRating null when <2 deliveries

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

database/migrations/2026_05_27_160000_extend_purchases_for_partial_receipt.php

@@ -0,0 +1,51 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('purchases', function (Blueprint $t) {
+            $t->foreignId('warehouse_id')->nullable()->after('supplier_id')
+                ->constrained('warehouses')->nullOnDelete();
+        });
+
+        Schema::table('purchase_items', function (Blueprint $t) {
+            $t->decimal('qty_received', 10, 2)->default(0)->after('qty');
+        });
+
+        // Backfill: items previously marked `received=true` were fully received.
+        DB::statement('UPDATE purchase_items SET qty_received = qty WHERE received = 1');
+
+        Schema::create('supplier_part_prices', function (Blueprint $t) {
+            $t->id();
+            $t->foreignId('company_id')->constrained()->cascadeOnDelete();
+            $t->foreignId('supplier_id')->constrained()->cascadeOnDelete();
+            $t->foreignId('part_id')->constrained()->cascadeOnDelete();
+            $t->foreignId('purchase_id')->nullable()->constrained()->nullOnDelete();
+            $t->decimal('price', 12, 2);
+            $t->string('currency', 6)->default('MDL');
+            $t->dateTime('observed_at');
+            $t->timestamps();
+
+            $t->index(['company_id', 'supplier_id', 'part_id', 'observed_at']);
+            $t->index(['company_id', 'part_id', 'observed_at']);
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('supplier_part_prices');
+        Schema::table('purchase_items', function (Blueprint $t) {
+            $t->dropColumn('qty_received');
+        });
+        Schema::table('purchases', function (Blueprint $t) {
+            $t->dropForeign(['warehouse_id']);
+            $t->dropColumn('warehouse_id');
+        });
+    }
+};