Add Restocking tab with demand-based order placement

[apeksha09]

Summary

• New /restocking route with budget slider and greedy item selection
• Recommendations based on demand forecasts vs on-hand inventory shortfall
• Place Order creates a Restocking order with 14-day lead time
• Orders tab updated with dedicated Restocking section and status badge
• EN/JP locale strings added for all new UI

Test plan

• Navigate to /restocking — budget slider, recommendations table, and Place Order button render correctly
• Adjust budget slider — selected items (green rows) update in real time
• Click Place Order — success message appears, order shows in Orders tab under Submitted Restocking Orders
• Verify 14-day expected delivery date on restocking orders
• Switch language to Japanese — all restocking strings display correctly

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