docs: mark PORTFOLIO-002 and PORTFOLIO-003 done, update roadmap

docs/roadmap/done/PORTFOLIO-003-physical-gold-premium-spread.yaml

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+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