feat: AI Desks — configurable agent system for news/technical/eco processing

- New ai_desks table with CRUD (get_all/by_type/upsert/delete)
- ai_desks router: REST API + GET /signal-catalog (7 extensible signals)
- News Desk: semantic dedup via AI (±N days window, system_prompt hint)
- Technical Desk: 4 signal detectors driven by desk config
  (ma_cross, rsi_extreme, bb_squeeze, new_52w_extreme)
- 3 more signals in catalog ready to enable: price_gap, volume_spike, macd_crossover
- market_event_detector.py loads desk configs at runtime, falls back to legacy params
- AIDesks.tsx: full editor UI with signal toggles, param sliders, instrument multi-select
- Sidebar: Bot icon + /ai-desks route

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

backend/main.py

@@ -8,6 +8,7 @@ from routers import instruments as instruments_router
 from routers import impact as impact_router
 from routers import cycle_actions as cycle_actions_router
 from routers import market_events as market_events_router
+from routers import ai_desks as ai_desks_router
 from routers import logs as logs_router
 from routers import var as var_router
 from routers import reports as reports_router
@@ -132,6 +133,7 @@ app.include_router(instruments_router.router)
 app.include_router(impact_router.router)
 app.include_router(cycle_actions_router.router)
 app.include_router(market_events_router.router)
+app.include_router(ai_desks_router.router)
 
 
 @app.get("/")