Investment portfolio charts, search fix, and holding creation fixes

- Add four portfolio charts: allocation donut by holding, allocation
  donut by asset type, cost basis vs current value bar, return % bar
- Fix asset search to use yf.Search() full-text instead of ticker-only
  lookup — name searches like "vanguard ftse all world" now work
- Fix holding creation double-quantity bug: holdings now created with
  quantity=0 so buy transaction is sole source of quantity/cost basis
- Add per-share / total price toggle in Add Holding modal with live
  calculated equivalent shown as you type
- Add ErrorBoundary in AppShell so render errors show a message instead
  of a blank page
- Fix donut charts using || instead of ?? when falling back from
  current_value to cost_basis_total (0 was not falling through ??)
- Allow HoldingCreate.quantity >= 0 (was gt=0) to support zero-init
- Fix error display for Pydantic v2 array-of-objects validation errors

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/services/price_feed_service.py

@@ -98,19 +98,26 @@ async def fetch_history(symbol: str, days: int = 365) -> list[dict]:
 def search_yahoo(query: str) -> list[dict]:
     try:
         import yfinance as yf
-        ticker = yf.Ticker(query)
-        info = ticker.fast_info
-        price = getattr(info, "last_price", None)
-        if price:
-            return [{
-                "symbol": query.upper(),
-                "name": getattr(info, "long_name", None) or query.upper(),
-                "type": "stock",
-                "currency": (getattr(info, "currency", None) or "USD").upper(),
-                "exchange": getattr(info, "exchange", None),
+        results = yf.Search(query, max_results=10).quotes
+        out = []
+        for r in results:
+            symbol = r.get("symbol")
+            if not symbol:
+                continue
+            quote_type = (r.get("quoteType") or r.get("typeDisp") or "stock").lower()
+            type_map = {"etf": "etf", "equity": "stock", "cryptocurrency": "crypto",
+                        "mutualfund": "fund", "bond": "bond"}
+            asset_type = type_map.get(quote_type, "stock")
+            out.append({
+                "symbol": symbol,
+                "name": r.get("longname") or r.get("shortname") or symbol,
+                "type": asset_type,
+                "currency": "USD",  # updated on first price sync
+                "exchange": r.get("exchDisp") or r.get("exchange"),
                 "data_source": "yahoo_finance",
                 "data_source_id": None,
-            }]
+            })
+        return out
     except Exception:
         pass
     return []