fix: apply Ganymede review fixes to portfolio code

dashboard_portfolio.py:
- datetime.utcnow() → datetime.now(timezone.utc) (deprecation fix)
- days parameter validation with try/except + min(..., 365) on 2 endpoints

fetch_coins.py:
- isinstance(chain, str) guard prevents AttributeError on string chain values
- Log when adjusted market cap differs from DexScreener value

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

diagnostics/dashboard_portfolio.py

@@ -8,7 +8,7 @@ import json
 import sqlite3
 import logging
 from html import escape as esc
-from datetime import datetime
+from datetime import datetime, timezone
 
 from aiohttp import web
 from shared_ui import render_page
@@ -304,7 +304,7 @@ async def handle_portfolio_page(request):
             d['nav_per_token'] = nav
             d['price_nav_ratio'] = ratio
             coins.append(d)
-        now = datetime.utcnow()
+        now = datetime.now(timezone.utc)
         html = render_portfolio_page(coins, now)
         return web.Response(text=html, content_type='text/html')
     finally:
@@ -315,7 +315,10 @@ async def handle_nav_ratios(request):
     """Server-side computed NAV ratios — only returns dates with valid data."""
     conn = _get_db(request)
     try:
-        days = int(request.query.get('days', '90'))
+        try:
+            days = min(int(request.query.get('days', '90')), 365)
+        except (ValueError, TypeError):
+            days = 90
         rows = conn.execute("""
             SELECT name, snapshot_date, price_usd, treasury_multisig_usd,
                    lp_usdc_total, adjusted_circulating_supply
@@ -355,7 +358,10 @@ async def handle_nav_ratios(request):
 async def handle_portfolio_history(request):
     conn = _get_db(request)
     try:
-        days = int(request.query.get('days', '90'))
+        try:
+            days = min(int(request.query.get('days', '90')), 365)
+        except (ValueError, TypeError):
+            days = 90
         rows = conn.execute("""
             SELECT * FROM coin_snapshots
             WHERE snapshot_date >= date('now', ? || ' days')

fetch_coins.py

@@ -92,6 +92,8 @@ def load_ownership_coins():
             continue
 
         chain = fm.get("chain") or {}
+        if isinstance(chain, str):
+            chain = {}
         raise_data = fm.get("raise") or {}
         ops = fm.get("operations") or {}
         liq = fm.get("liquidation") or {}
@@ -563,8 +565,12 @@ def compute_derived(row, coin):
     if adj_circ and adj_circ > 0:
         row["effective_liq_price"] = cash_total / adj_circ
         if price and price > 0:
+            original_mcap = row.get("market_cap_usd")
             row["market_cap_usd"] = price * adj_circ
             mcap = row["market_cap_usd"]
+            if original_mcap and abs(mcap - original_mcap) > 1:
+                logger.debug("%s: adjusted mcap $%.0f (was $%.0f, protocol_owned=%s)",
+                             row.get("name", "?"), mcap, original_mcap, protocol_tokens)
     if price and price > 0 and row.get("effective_liq_price"):
         row["delta_pct"] = ((row["effective_liq_price"] / price) - 1) * 100