Add activation thresholds: qualified-signal defaults and views

Admin-configurable thresholds (min R:R, default 2.0; min confidence,
default 70%) defining what counts as an actionable signal:

- Admin Settings: new Activation Thresholds panel
  (GET/PUT /admin/settings/activation)
- GET /trades/activation exposes values to all users with access
- Signals/Setups: filters initialize from activation values
- Track Record: "Qualified signals only" toggle (default on) via
  min_rr/min_confidence params on /trades/performance; the
  confidence breakdown always covers the full population so the
  thresholds can be validated against outcomes
- Dashboard: "Qualified" metric and qualified-first Top Setups
- Outcome evaluator unchanged: every setup is still evaluated

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/routers/admin.py

@@ -9,6 +9,7 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from app.dependencies import get_db, require_admin
 from app.models.user import User
 from app.schemas.admin import (
+    ActivationConfigUpdate,
     CreateUserRequest,
     DataCleanupRequest,
     JobToggle,
@@ -148,6 +149,28 @@ async def update_recommendation_settings(
     return APIEnvelope(status="success", data=updated)
 
 
+@router.get("/admin/settings/activation", response_model=APIEnvelope)
+async def get_activation_settings(
+    _admin: User = Depends(require_admin),
+    db: AsyncSession = Depends(get_db),
+):
+    config = await admin_service.get_activation_config(db)
+    return APIEnvelope(status="success", data=config)
+
+
+@router.put("/admin/settings/activation", response_model=APIEnvelope)
+async def update_activation_settings(
+    body: ActivationConfigUpdate,
+    _admin: User = Depends(require_admin),
+    db: AsyncSession = Depends(get_db),
+):
+    updated = await admin_service.update_activation_config(
+        db,
+        body.model_dump(exclude_unset=True, exclude_none=True),
+    )
+    return APIEnvelope(status="success", data=updated)
+
+
 @router.get("/admin/settings/ticker-universe", response_model=APIEnvelope)
 async def get_ticker_universe_setting(
     _admin: User = Depends(require_admin),