feat: dynamic market ticker watchlist (Markets page)

Add ability to add/remove custom tickers (e.g. EURCHF=X) on the
Markets & Prices page without editing config. Tickers are validated
via yfinance, persisted in market_watchlist SQLite table, merged into
the quotes feed as a 'custom' group, and shown in a dedicated tab
with per-card remove buttons.

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

backend/routers/market_data.py

@@ -39,6 +39,38 @@ def watchlist():
     return WATCHLIST
 
 
+@router.get("/custom-tickers")
+def list_custom_tickers():
+    from services.database import get_market_custom_tickers
+    return get_market_custom_tickers()
+
+
+@router.post("/custom-tickers/{ticker}")
+def add_custom_ticker(ticker: str):
+    from services.data_fetcher import get_quote
+    from services.database import add_market_custom_ticker
+    import yfinance as yf
+    ticker = ticker.strip().upper()
+    q = get_quote(ticker)
+    if not q or not q.get("price"):
+        from fastapi import HTTPException
+        raise HTTPException(400, f"Ticker '{ticker}' not found on yfinance")
+    try:
+        info = yf.Ticker(ticker).fast_info
+        name = getattr(info, "long_name", None) or getattr(info, "short_name", None) or ticker
+    except Exception:
+        name = ticker
+    add_market_custom_ticker(ticker, name)
+    return {"ticker": ticker, "name": name, "price": q["price"]}
+
+
+@router.delete("/custom-tickers/{ticker}")
+def remove_custom_ticker(ticker: str):
+    from services.database import remove_market_custom_ticker
+    remove_market_custom_ticker(ticker.strip().upper())
+    return {"removed": ticker.upper()}
+
+
 @router.get("/validate")
 def validate_ticker(symbol: str = Query(..., description="Ticker to validate against yfinance")):
     """Check if a ticker is fetchable. Returns valid=True + live price/name, or valid=False + reason."""