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/services/database.py

@@ -91,6 +91,12 @@ def init_db():
         # Regime / counter-scenario architecture
         "ALTER TABLE custom_patterns ADD COLUMN regime_tag TEXT",
         "ALTER TABLE custom_patterns ADD COLUMN counter_of TEXT",
+        # Markets & Prices — user-defined watchlist
+        """CREATE TABLE IF NOT EXISTS market_watchlist (
+            ticker TEXT PRIMARY KEY,
+            name TEXT,
+            added_at TEXT DEFAULT (datetime('now'))
+        )""",
     ]:
         try:
             c.execute(_sql)
@@ -2307,6 +2313,42 @@ def remove_watchlist_ticker(ticker: str) -> bool:
     return changed
 
 
+# ── Market Watchlist (user-added tickers for Markets page) ───────────────────
+
+def get_market_custom_tickers() -> List[Dict]:
+    conn = get_conn()
+    rows = conn.execute(
+        "SELECT ticker, name, added_at FROM market_watchlist ORDER BY added_at ASC"
+    ).fetchall()
+    conn.close()
+    return [dict(r) for r in rows]
+
+
+def add_market_custom_ticker(ticker: str, name: str = "") -> bool:
+    conn = get_conn()
+    try:
+        conn.execute(
+            "INSERT OR IGNORE INTO market_watchlist (ticker, name) VALUES (?, ?)",
+            (ticker.upper(), name),
+        )
+        inserted = conn.total_changes > 0
+        conn.commit()
+    except Exception:
+        inserted = False
+    finally:
+        conn.close()
+    return inserted
+
+
+def remove_market_custom_ticker(ticker: str) -> bool:
+    conn = get_conn()
+    conn.execute("DELETE FROM market_watchlist WHERE ticker=?", (ticker.upper(),))
+    changed = conn.total_changes > 0
+    conn.commit()
+    conn.close()
+    return changed
+
+
 # ── System Logs ───────────────────────────────────────────────────────────────
 
 def log_system_event(