feat: Forex Factory calendar — unified past+future list style Trading Economics

- New ff_calendar table (event_date, time, currency, impact, actual, forecast, previous)
- New service ff_calendar.py: bulk CSV import (83K events 2007-2025) + live sync
  from faireconomy.media JSON endpoint (this week / next week)
- New API endpoints: POST /api/eco/ff-import, POST /api/eco/ff-sync,
  GET /api/eco/calendar (period filter), GET /api/eco/ff-stats
- CalendarPage.tsx full rewrite: period tabs (Recent/Today/Tomorrow/This Week…),
  currency flags filter, impact filter, unified date-grouped table with
  Time·Flag·Currency·Impact·Event·Actual·Forecast·Previous columns,
  green/red actual vs forecast, TODAY badge, auto-refresh 60s

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

backend/services/database.py

@@ -685,6 +685,29 @@ def init_db():
     except Exception:
         pass
 
+    # ── Forex Factory Calendar ─────────────────────────────────────────────────
+    c.execute("""CREATE TABLE IF NOT EXISTS ff_calendar (
+        id INTEGER PRIMARY KEY AUTOINCREMENT,
+        event_date TEXT NOT NULL,
+        event_time TEXT,
+        currency TEXT NOT NULL,
+        impact TEXT,
+        event_name TEXT NOT NULL,
+        actual_value TEXT,
+        forecast_value TEXT,
+        previous_value TEXT,
+        detail TEXT,
+        source TEXT DEFAULT 'ff_cache',
+        fetched_at TEXT DEFAULT (datetime('now')),
+        UNIQUE(event_date, event_time, currency, event_name)
+    )""")
+    try:
+        c.execute("CREATE INDEX IF NOT EXISTS idx_ff_date ON ff_calendar(event_date)")
+        c.execute("CREATE INDEX IF NOT EXISTS idx_ff_currency ON ff_calendar(currency)")
+        c.execute("CREATE INDEX IF NOT EXISTS idx_ff_impact ON ff_calendar(impact)")
+    except Exception:
+        pass
+
     # ── Specialist Desks ───────────────────────────────────────────────────────
     c.execute("""CREATE TABLE IF NOT EXISTS specialist_reports (
         id TEXT PRIMARY KEY,