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>

frontend/src/components/admin/ActivationSettings.tsx

@@ -7,7 +7,6 @@ const DEFAULTS: ActivationConfig = {
   min_momentum_percentile: 80,
   min_rr: 1.2,
   min_confidence: 55,
-  min_target_probability: 0,
   require_high_conviction: false,
   exclude_conflicts: false,
 };
@@ -91,20 +90,7 @@ export function ActivationSettings() {
       <div className="border-t border-white/[0.06] pt-4">
         <p className="text-xs font-medium uppercase tracking-widest text-gray-500">Optional tighteners</p>
         <p className="mt-1 text-[11px] text-gray-600">Off by default — turn on to be more selective on top of the momentum gate.</p>
-        <div className="mt-3 grid gap-3 md:grid-cols-3">
-          <label className="block space-y-1">
-            <span className="text-xs text-gray-400">Min Target Probability (%)</span>
-            <input
-              type="number"
-              min={0}
-              max={100}
-              step={1}
-              value={form.min_target_probability}
-              onChange={(e) => setForm((prev) => ({ ...prev, min_target_probability: Number(e.target.value) }))}
-              className="w-full input-glass px-3 py-2 text-sm"
-            />
-            <span className="text-[11px] text-gray-600">Best target's probability must clear this. 0 disables.</span>
-          </label>
+        <div className="mt-3 grid gap-3 md:grid-cols-2">
           <label className="flex cursor-pointer items-start gap-2.5 text-sm text-gray-300">
             <input
               type="checkbox"