Show DTE per leg + per-expiry remaining DTE for multi-expiry strategies

- Legs table: small DTE chip next to each leg's expiry (e.g. "14d", "<1d",
  "exp" — absolute days from today)
- Chart header: when active legs span multiple expiries (calendar/diagonal),
  a "Remaining: 2026-05-15 (0d) · 2026-06-20 (36d)" line shows how many
  days each unique expiry has left at the current slider position

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/strategy.html

@@ -109,11 +109,12 @@
                   <button class="btn btn-outline-secondary" @click="zoomFit()" title="Reset pan & zoom">Fit</button>
                 </div>
                 <!-- time slider -->
-                <div class="d-flex align-items-center gap-2" style="min-width:300px;">
+                <div class="d-flex align-items-center flex-wrap gap-2" style="min-width:300px;">
                   <span class="text-secondary small text-nowrap">Now</span>
                   <input type="range" class="form-range" min="0" :max="maxDTE" step="1" x-model.number="dteOffset" @input="scheduleRender()" style="min-width:150px;">
                   <span class="text-secondary small text-nowrap">Exp</span>
                   <span class="badge bg-blue-lt text-nowrap" x-text="dteLabel"></span>
+                  <small class="text-secondary w-100" x-show="hasMultiExpiry" x-text="'Remaining: ' + expiryBreakdown"></small>
                 </div>
               </div>
             </div>
@@ -173,11 +174,14 @@
                         </select>
                         <span x-show="!hasStrikeOpts(lv)" x-text="lv.strike"></span>
                       </td>
-                      <td class="mono small" style="width:8.5rem">
+                      <td class="mono small" style="width:11rem">
+                        <div class="d-flex align-items-center gap-1 flex-nowrap">
                           <select x-show="hasExpiryOpts(lv)" class="form-select form-select-sm" :value="lv.expiry" @change="changeExpiry(lv.id, $event.target.value)" title="Change expiry — strike, entry, IV & mark update from the new chain">
                             <template x-for="e in expiryOpts(lv)" :key="e"><option :value="e" x-text="e"></option></template>
                           </select>
                           <span x-show="!hasExpiryOpts(lv)" x-text="lv.expiry"></span>
+                          <span class="badge bg-secondary-lt text-secondary" :title="'Days to expiry from today'" x-text="legDTEStr(lv)"></span>
+                        </div>
                       </td>
                       <td style="width:8.5rem">
                         <div class="input-group input-group-sm flex-nowrap">
@@ -493,6 +497,22 @@
           if (this.dteOffset === 0) return 'Today (' + ds + ')';
           return 'T+' + this.dteOffset + 'd · ' + ds;
         },
+        get hasMultiExpiry() {
+          return new Set(this.activeLegs.map(l => l.expiry)).size > 1;
+        },
+        get expiryBreakdown() {
+          const uniq = [...new Set(this.activeLegs.map(l => l.expiry))].sort();
+          return uniq.map(e => {
+            const rem = Math.max(0, Math.round(legDTE({expiry:e}) - this.dteOffset));
+            return e + ' (' + rem + 'd)';
+          }).join(' · ');
+        },
+        legDTEStr(lv) {
+          const d = legDTE(lv);
+          if (d < 0) return 'exp';
+          if (d < 1) return '<1d';
+          return Math.round(d) + 'd';
+        },
 
         get legsView() {
           return this.legs.map(l => {