feat: replace Trading Economics with FMP for upcoming calendar forecasts

TE costs $199/month and its Economic Calendar is not in the free tier.
FMP (Financial Modeling Prep) offers a free API key (250 req/day) with
full economic calendar coverage including consensus estimates (forecasts).

- Add backend/services/fmp_calendar.py: fetches upcoming events from
  GET /api/v3/economic_calendar (one request, all countries, date range)
- Replace /api/eco/te-key + te-sync endpoints with fmp-key + fmp-sync
- Update daily background sync in main.py to use fmp_calendar
- Replace TEPanel with FMPPanel in CalendarPage.tsx (link to FMP docs)
- Remove broken Cloudflare-blocked FF HTML scrape button from ImportPanel

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

backend/main.py

@@ -109,15 +109,15 @@ def startup():
                 print(f"[Daily] FF live sync error: {e}", flush=True)
 
             try:
-                # Trading Economics — upcoming forecasts (only if key is set)
+                # FMP — upcoming forecasts (only if key is set)
                 from services.database import get_config
-                te_key = get_config("te_api_key") or ""
-                if te_key:
-                    from services.te_calendar import fetch_upcoming
+                fmp_key = get_config("fmp_api_key") or ""
+                if fmp_key:
+                    from services.fmp_calendar import fetch_upcoming
                     r = fetch_upcoming(weeks_ahead=6)
-                    print(f"[Daily] TE sync: {r.get('total_upserted', 0)} upserted", flush=True)
+                    print(f"[Daily] FMP sync: {r.get('total_upserted', 0)} upserted", flush=True)
             except Exception as e:
-                print(f"[Daily] TE sync error: {e}", flush=True)
+                print(f"[Daily] FMP sync error: {e}", flush=True)
 
             _time.sleep(86400)  # repeat every 24h