Stage 5.1 — Warehouse ERP: batches + FIFO + reservations + multi-warehouse

Schema:
- warehouses (multi-warehouse, code unique per company, is_default)
- part_batches (lot per receipt, qty_in/qty_remaining, buy_price, FIFO-indexed)
- warehouse_events (immutable ledger: opening/receipt/issue/transfer/adjustment/write_off)
- part_reservations (per-WO allocations from specific batches, active/consumed/released)
- companies.default_warehouse_id + parts.qty_reserved

Backfill: 1 default warehouse + 1 opening batch per existing part per company.

WarehouseService:
- receive / issue (FIFO) / reserve / release / consume / transfer / adjust
- DB::transaction + lockForUpdate on batch rows
- InsufficientStockException with requested + available context
- Auto-syncs parts.qty as aggregate cache (source of truth = sum(qty_remaining))

WO integration:
- WorkOrderPart created/updated → reserve from FIFO batches
- WorkOrderPart deleted → release
- WorkOrder status=done → consume reservations into issue events
- WorkOrder status=cancelled → release reservations

Filament:
- WarehouseResource (CRUD)
- BatchesRelationManager on PartResource (FIFO list with qty_remaining + cost)
- "Recepție" action on parts list → calls WarehouseService::receive
- qty_reserved column added on parts list

Tests (8 new, all pass):
- receipt creates batch + event
- FIFO order verified across 3 batches with different received_at
- InsufficientStockException on over-issue
- Reservations block other reservations but don't deplete on-hand
- WO done consumes; WO cancelled releases
- Batches tenant-isolated
- Transfer between warehouses with weighted-avg cost

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

app/Filament/Tenant/Resources/PartResource/RelationManagers/BatchesRelationManager.php

@@ -0,0 +1,45 @@
+<?php
+
+namespace App\Filament\Tenant\Resources\PartResource\RelationManagers;
+
+use Filament\Resources\RelationManagers\RelationManager;
+use Filament\Tables;
+use Filament\Tables\Table;
+
+class BatchesRelationManager extends RelationManager
+{
+    protected static string $relationship = 'batches';
+
+    protected static ?string $title = 'Loturi (FIFO)';
+
+    public function table(Table $table): Table
+    {
+        return $table
+            ->columns([
+                Tables\Columns\TextColumn::make('received_at')
+                    ->label('Recepție')
+                    ->dateTime('d.m.Y H:i')
+                    ->sortable(),
+                Tables\Columns\TextColumn::make('warehouse.code')->label('Depozit')->placeholder('—'),
+                Tables\Columns\TextColumn::make('batch_ref')->label('Ref.')->placeholder('—'),
+                Tables\Columns\TextColumn::make('supplier.name')->label('Furnizor')->placeholder('—'),
+                Tables\Columns\TextColumn::make('qty_in')
+                    ->label('Intrat')
+                    ->numeric(decimalPlaces: 2)
+                    ->alignRight(),
+                Tables\Columns\TextColumn::make('qty_remaining')
+                    ->label('Rămas')
+                    ->numeric(decimalPlaces: 2)
+                    ->alignRight()
+                    ->weight('bold')
+                    ->color(fn ($state) => (float) $state <= 0 ? 'gray' : 'success'),
+                Tables\Columns\TextColumn::make('buy_price')
+                    ->label('Preț unit.')
+                    ->money('MDL')
+                    ->alignRight(),
+            ])
+            ->defaultSort('received_at')
+            ->emptyStateHeading('Niciun lot înregistrat')
+            ->emptyStateDescription('Apasă „Recepție" pe lista de piese pentru a înregistra prima intrare în depozit.');
+    }
+}