fix: custom tickers now placed in their natural asset-class tab

- Detect yfinance quote_type (CURRENCY→forex, FUTURE→energy, INDEX→indices,
  ETF→etfs, EQUITY→equities) when adding a custom ticker and persist it in
  market_watchlist.asset_class
- get_all_quotes() merges custom tickers into their proper group (e.g. EURUSD=X
  appears under Forex) instead of always under a separate "Custom" group
- "Custom" tab only shows tickers whose type couldn't be detected
- Add market_watchlist.asset_class migration; ensure backtest_lab_runs and
  market_watchlist are always created at init_db() time

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

backend/routers/market_data.py

@@ -45,6 +45,16 @@ def list_custom_tickers():
     return get_market_custom_tickers()
 
 
+_QUOTE_TYPE_TO_ASSET_CLASS = {
+    "CURRENCY": "forex",
+    "FUTURE": "energy",
+    "INDEX": "indices",
+    "ETF": "etfs",
+    "EQUITY": "equities",
+    "MUTUALFUND": "etfs",
+}
+
+
 @router.post("/custom-tickers/{ticker}")
 def add_custom_ticker(ticker: str):
     from services.data_fetcher import get_quote
@@ -55,13 +65,17 @@ def add_custom_ticker(ticker: str):
     if not q or not q.get("price"):
         from fastapi import HTTPException
         raise HTTPException(400, f"Ticker '{ticker}' not found on yfinance")
+    name = ticker
+    asset_class = "custom"
     try:
         info = yf.Ticker(ticker).fast_info
         name = getattr(info, "long_name", None) or getattr(info, "short_name", None) or ticker
+        quote_type = getattr(info, "quote_type", "") or ""
+        asset_class = _QUOTE_TYPE_TO_ASSET_CLASS.get(quote_type.upper(), "custom")
     except Exception:
-        name = ticker
-    add_market_custom_ticker(ticker, name)
-    return {"ticker": ticker, "name": name, "price": q["price"]}
+        pass
+    add_market_custom_ticker(ticker, name, asset_class)
+    return {"ticker": ticker, "name": name, "asset_class": asset_class, "price": q["price"]}
 
 
 @router.delete("/custom-tickers/{ticker}")