feat(HRT-79): alertes Telegram configurables Premium/Pro

- telegram_alerts.py: service envoi alertes via Bot API (send_pre_race_alerts,
  build_race_alert, send_telegram_message) — gestion gracieuse TELEGRAM_BOT_TOKEN absent
- auth_db.py: migrate_telegram_columns() idempotente (ALTER TABLE + try/except OperationalError)
  colonnes: telegram_chat_id, alert_value_bets, alert_top1, alert_quinte_only
- api_v1/routes/user.py: blueprint user_bp GET/POST /api/v1/user/telegram-config
  protégé @jwt_required_middleware + @plan_required('premium','pro')
- api_v1/__init__.py: import + register user_bp
- turf_scheduler.py: run_telegram_alerts() + schedule_dynamic_telegram_alerts()
  planifiées 30min avant course (même pattern que schedule_dynamic_scoring)
  avec try/except Exception + fallback logger

Co-Authored-By: Paperclip <noreply@paperclip.ing>

api_v1/__init__.py

@@ -3,6 +3,7 @@
 API v1 Blueprint package — Turf SaaS
 Sprint 3-4: HRT-29 — Refacto API /v1/
 Sprint 5-6: HRT-31 — Billing Stripe
+HRT-79: Alertes Telegram configurables (user blueprint)
 
 Registers sub-blueprints:
   /api/v1/health      — public health-check
@@ -13,6 +14,7 @@ Registers sub-blueprints:
   /api/v1/export/     — export CSV (pro)
   /api/v1/metrics     — métriques perf ML (premium+)
   /api/v1/billing/    — Stripe checkout, portal, webhook, status
+  /api/v1/user/       — config utilisateur, alertes Telegram (premium+)
   /api/v1/docs        — Swagger UI (via flasgger, registered on app)
 """
 
@@ -26,6 +28,7 @@ from .routes.backtest import backtest_bp
 from .routes.export import export_bp
 from .routes.metrics import metrics_bp
 from .routes.billing import billing_bp
+from .routes.user import user_bp
 
 # Master blueprint that aggregates all sub-routes under /api/v1
 api_v1_bp = Blueprint("api_v1", __name__, url_prefix="/api/v1")
@@ -41,3 +44,4 @@ def register_api_v1(app):
     app.register_blueprint(export_bp)
     app.register_blueprint(metrics_bp)
     app.register_blueprint(billing_bp)
+    app.register_blueprint(user_bp)