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>

app/schemas/admin.py

@@ -62,7 +62,6 @@ class ActivationConfigUpdate(BaseModel):
     min_momentum_percentile: float | None = Field(default=None, ge=0, le=100)
     min_rr: float | None = Field(default=None, ge=0)
     min_confidence: float | None = Field(default=None, ge=0, le=100)
-    min_target_probability: float | None = Field(default=None, ge=0, le=100)
     require_high_conviction: bool | None = None
     exclude_conflicts: bool | None = None