id: PORTFOLIO-003
title: Physical Gold Premium and Spread
status: backlog
priority: P1
size: S
depends_on:
  - PORTFOLIO-001
tags: [portfolio, physical-gold]
summary: Support dealer premium and bid/ask spread for physical gold positions.
acceptance_criteria:
  - Position can specify `purchase_premium` (dealer markup over spot)
  - Position can specify `bid_ask_spread` (expected sale discount below spot)
  - True cost basis = entry_price + purchase_premium
  - Effective exit value = spot - bid_ask_spread
  - P&L shows both paper P&L and realized P&L accounting for spread
  - Default premium/spread values for common products (coins, bars)
  - Settings page exposes premium/spread inputs for XAU positions
notes:
  - Common gold products:
    - Gold ETF (GLD): 0% premium (market price), spread ~0.1%
    - Gold coins (1oz): 3-5% premium, 2-4% spread
    - Gold bars (1kg): 1-2% premium, 1-2% spread
    - Allocated storage (Goldmoney, BullionVault): 0.1% premium, 0.3% spread
  - Premium lowers effective entry price
  - Spread lowers effective exit price
implementation_hints:
  - Add `purchase_premium: Decimal | None` to `Position` (percentage)
  - Add `bid_ask_spread: Decimal | None` to `Position` (percentage)
  - Cost basis formula: `effective_entry = spot_at_entry × (1 + premium)`
  - Exit value formula: `effective_exit = current_spot × (1 - spread)`
  - Add premium/spread presets to settings UI