Fix sidebar username, Signals filter clarity and layout

- JWT now carries a username claim; sidebar shows "Signed in as <name>"
  instead of the bare user id (sub). Re-login required for the new claim.
- Signals: Min R:R / Min Confidence inputs reflect the effective filter —
  auto-filled from the activation gate when "Qualified only" is on, reset
  to 0 when off (no more misleading 0 while the gate is active).
- Signals layout: Run Scanner moved to its own action row (it's a job
  trigger, not a filter); qualified toggle grouped with the refinement
  filters under one Filters panel.

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

tests/unit/test_recommendation_service.py

@@ -5,6 +5,7 @@ from dataclasses import dataclass
 from app.services.recommendation_service import (
     _build_reasoning,
     _choose_recommended_action,
+    _select_primary_target,
     direction_analyzer,
     probability_estimator,
     signal_conflict_detector,
@@ -102,6 +103,31 @@ def test_reasoning_explains_missing_setup():
     assert "no high-conviction long setup" in reasoning.lower()
 
 
+def test_primary_target_is_most_likely_worthwhile_not_lottery():
+    targets = [
+        {"price": 110.0, "rr_ratio": 2.0, "probability": 65.0},   # worthwhile, most likely ← primary
+        {"price": 120.0, "rr_ratio": 3.5, "probability": 50.0},
+        {"price": 140.0, "rr_ratio": 6.0, "probability": 15.0},   # far lottery — not chosen
+    ]
+    primary = _select_primary_target(targets)
+    assert primary is not None
+    assert primary["price"] == 110.0
+
+
+def test_primary_target_skips_sub_threshold_rr():
+    targets = [
+        {"price": 102.0, "rr_ratio": 1.0, "probability": 95.0},   # high prob but trivial R:R — skipped
+        {"price": 115.0, "rr_ratio": 2.5, "probability": 60.0},   # most likely above the R:R floor ← primary
+    ]
+    primary = _select_primary_target(targets)
+    assert primary is not None
+    assert primary["price"] == 115.0
+
+
+def test_primary_target_none_when_empty():
+    assert _select_primary_target([]) is None
+
+
 def test_detects_sentiment_technical_conflict():
     conflicts = signal_conflict_detector.detect_conflicts(
         dimension_scores={"technical": 72.0, "momentum": 55.0, "fundamental": 50.0},