Replace drag-pan with ‹ / › buttons in the chart header

Removed click-and-drag panning; the chart header now has ‹ and › buttons
that shift the price window left/right by ~40% of the current half-width
per click. Fit still re-centres and resets zoom.

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

frontend/strategy.html

@@ -99,12 +99,14 @@
             <div class="card-header d-flex align-items-center justify-content-between flex-wrap gap-3">
               <h3 class="card-title text-white mb-0">Profit / Loss vs. Underlying Price</h3>
               <div class="d-flex align-items-center flex-wrap gap-3">
-                <!-- price-range zoom -->
+                <!-- pan + zoom price range -->
-                <div class="btn-group btn-group-sm" role="group" aria-label="Zoom price range">
+                <div class="btn-group btn-group-sm" role="group" aria-label="Pan and zoom price range">
+                  <button class="btn btn-outline-secondary" @click="panLeft()" title="Move left — show lower prices">‹</button>
                   <button class="btn btn-outline-secondary" @click="zoomOut()" title="Zoom out — wider price range">−</button>
                   <button class="btn btn-outline-secondary" disabled style="min-width:5rem" x-text="'±' + lastHalfPct + '%'"></button>
                   <button class="btn btn-outline-secondary" @click="zoomIn()" title="Zoom in — narrower price range">+</button>
-                  <button class="btn btn-outline-secondary" @click="zoomFit()" title="Reset zoom">Fit</button>
+                  <button class="btn btn-outline-secondary" @click="panRight()" title="Move right — show higher prices">›</button>
+                  <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;">
@@ -116,9 +118,7 @@
               </div>
             </div>
             <div class="card-body p-0">
-              <div id="plChart" :style="'min-height:380px;user-select:none;cursor:' + (_drag ? 'grabbing' : 'grab')"
+              <div id="plChart" style="min-height:380px;" role="img" aria-label="Profit and loss diagram"></div>
-                   @mousedown="startPan($event)" @mousemove.window="onPan($event)" @mouseup.window="endPan()" @mouseleave.window="endPan()"
-                   role="img" aria-label="Profit and loss diagram (drag left/right to pan the price range)"></div>
             </div>
           </div>
 
@@ -318,7 +318,6 @@
         symbol: '', symbols: [], spot: 0, legs: [],
         dteOffset: 0,
         xZoom: 1, xPan: 0, lastHalfPct: 0,
-        _drag: null,
         refreshing: false, showManual: false, toast: '',
         manual: { side:'long', type:'call', qty:1, strike:null, expiry:'', entryPrice:null, ivPct:null },
         chart: null, _renderTimer: null,
@@ -587,22 +586,9 @@
         zoomIn()  { this.xZoom = Math.max(0.2, +(this.xZoom / 1.4).toFixed(3)); this.renderChart(); },
         zoomOut() { this.xZoom = Math.min(8,   +(this.xZoom * 1.4).toFixed(3)); this.renderChart(); },
         zoomFit() { this.xZoom = 1; this.xPan = 0; this.renderChart(); },
-
+        _panStep() { return 0.4 * (this._lastHalf || (Math.max(this.spot, 1) * 0.22)); },
-        // click-and-drag to pan the price window
+        panLeft()  { this.xPan -= this._panStep(); this.renderChart(); },
-        startPan(e) {
+        panRight() { this.xPan += this._panStep(); this.renderChart(); },
-          if (e.button !== 0) return;
-          const pw = (this._lastPlotW && this._lastPlotW > 50) ? this._lastPlotW
-            : ((document.getElementById('plChart')?.clientWidth || 600) - 70);
-          this._drag = { x: e.clientX, pan: this.xPan || 0, half: this._lastHalf || ((this.spot || 100) * 0.22), pw };
-          e.preventDefault();
-        },
-        onPan(e) {
-          if (!this._drag) return;
-          const dx = e.clientX - this._drag.x;            // drag right -> show lower prices
-          this.xPan = this._drag.pan - (dx / this._drag.pw) * (2 * this._drag.half);
-          this.scheduleRender();
-        },
-        endPan() { if (this._drag) this._drag = null; },
 
         renderChart() {
           const legs = this.activeLegs, net = this.netCost;
@@ -711,11 +697,6 @@
             this.chart = new ApexCharts(document.getElementById('plChart'), opts);
             this.chart.render();
           }
-          // remember the plot-area width for drag-to-pan math
-          try {
-            const gw = this.chart && this.chart.w && this.chart.w.globals && this.chart.w.globals.gridWidth;
-            this._lastPlotW = (gw && gw > 50) ? gw : ((document.getElementById('plChart')?.clientWidth || 600) - 70);
-          } catch {}
         },
 
         fmtMoney,