remove min_target_probability gate + add chart time-range presets

min_target_probability is gone: it filtered on the probability model the
calibration has repeatedly shown to be weak and overconfident, it was redundant
with the momentum gate, and as an off-by-default knob it just invited bad tuning.
Removed from the backend gate, activation config/schema, the frontend mirror
(qualifiesSetup / activationSummary), and ActivationSettings. The probability
model stays where it does real work (primary-target selection + display).

Charts: with multi-year history the all-bars default was unreadable. Added
time-range presets (1M / 3M / 6M / YTD / 1Y / 3Y / 5Y / All), defaulting to 1Y;
clicking a preset always re-applies (snaps back after a manual zoom). Y-axis
autoscale and wheel-zoom / drag-pan were already there.

339 backend tests pass; frontend build clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/unit/test_qualification.py

@@ -12,7 +12,6 @@ DEFAULT_GATE = {
     "min_momentum_percentile": 0.0,
     "min_rr": 1.2,
     "min_confidence": 55.0,
-    "min_target_probability": 0.0,
     "require_high_conviction": False,
     "exclude_conflicts": False,
 }
@@ -25,7 +24,6 @@ STRICT_GATE = {
     "min_momentum_percentile": 0.0,
     "min_rr": 2.0,
     "min_confidence": 70.0,
-    "min_target_probability": 60.0,
     "require_high_conviction": True,
     "exclude_conflicts": True,
 }
@@ -112,9 +110,6 @@ class TestStrictTighteners:
         s = _setup(risk_level="Medium", targets=[{"probability": 65.0, "is_primary": True}])
         assert setup_qualifies(s, STRICT_GATE) is False
 
-    def test_low_target_probability_fails(self):
-        assert setup_qualifies(_setup(targets=[{"probability": 40.0, "is_primary": True}]), STRICT_GATE) is False
-
 
 class TestBestTargetProbability:
     def test_returns_max(self):