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/schemas/admin.py

@@ -56,3 +56,9 @@ class RecommendationConfigUpdate(BaseModel):
 
 class TickerUniverseUpdate(BaseModel):
     universe: Literal["sp500", "nasdaq100", "nasdaq_all"]
+
+
+class ActivationConfigUpdate(BaseModel):
+    """Activation thresholds: what counts as an actionable signal."""
+    min_rr: float | None = Field(default=None, ge=0)
+    min_confidence: float | None = Field(default=None, ge=0, le=100)