feat: Phase 2 — economic event surprise tracker (FRED actuals + z-score)

- economic_events table in DB (series_id, actual, forecast_baseline, surprise_pct, surprise_zscore, direction)
- DB helpers: save_economic_event(), get_recent_economic_surprises(), get_economic_events_for_calendar()
- fred_fetcher.py: _compute_zscore_surprise() computes 12-period MA as implied consensus + z-score deviation; save_fred_releases_to_db() persists releases per cycle; build_economic_surprise_block() formats significant surprises for AI prompt
- auto_cycle.py: saves FRED releases to economic_events each cycle, appends surprise block to fred_block for injection into both suggestion and scoring prompts
- data_fetcher.py: get_economic_calendar() now merges static upcoming events with past FRED actuals from DB (Prev/Fcst/Actual/z-score fields populated)
- CalendarPage.tsx: past events show colored z-score badge (⚡ for |z|≥1.5, bullish/bearish colors)
- EconomicEvent type: added surprise_zscore, surprise_direction, source fields

Activates automatically once fred_api_key is set in Configuration.

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

frontend/src/types/index.ts

@@ -124,6 +124,9 @@ export interface EconomicEvent {
   previous?: string
   forecast?: string
   actual?: string
+  surprise_zscore?: number
+  surprise_direction?: 'bullish' | 'bearish' | 'neutral'
+  source?: string
 }
 
 export interface HistoricalCandle {