feat: FASE 5b/6.1+6.2 - SPC Backend + Dashboard Metrologist (Plotly.js)

Aggiunge servizio SPC con calcoli Cp/Cpk/Pp/Ppk, carta di controllo (UCL/LCL),
istogramma con curva normale. Router FastAPI con 5 endpoint statistics, blueprint
Flask con proxy AJAX, dashboard interattiva Alpine.js + Plotly.js con filtri per
ricetta/subtask/date, riepilogo pass/fail, gauge Cpk e i18n IT/EN completo.

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

client/static/js/numpad.js

@@ -13,6 +13,10 @@ function numpad() {
     maxIntDigits: 6,     // Maximum integer digits
     maxDecDigits: 6,     // Maximum decimal digits
 
+    // HID burst detection (USB caliper vs manual typing)
+    _lastKeyTime: 0,     // Timestamp of last keystroke
+    _burstCount: 0,      // Consecutive fast keystrokes
+
     /**
      * Get the display value with sign
      */
@@ -115,11 +119,16 @@ function numpad() {
 
       const val = this.numericValue;
 
+      // Determine input method: 3+ fast keystrokes = USB caliper burst
+      const inputMethod = this._burstCount >= 3 ? 'usb_caliper' : 'manual';
+
       // Dispatch custom event for parent component to handle
-      this.$dispatch('numpad-confirm', { value: val });
+      this.$dispatch('numpad-confirm', { value: val, inputMethod: inputMethod });
 
       // Reset after confirmation
       this.clearAll();
+      this._burstCount = 0;
+      this._lastKeyTime = 0;
     },
 
     /**
@@ -157,11 +166,13 @@ function numpad() {
       // Number keys
       if (e.key >= '0' && e.key <= '9') {
         e.preventDefault();
+        this._trackBurst();
         this.addDigit(e.key);
       }
       // Decimal point (both . and ,)
       else if (e.key === '.' || e.key === ',') {
         e.preventDefault();
+        this._trackBurst();
         this.addDecimal();
       }
       // Backspace
@@ -184,6 +195,24 @@ function numpad() {
         e.preventDefault();
         this.toggleSign();
       }
+    },
+
+    /**
+     * Track keystroke timing for HID burst detection.
+     * USB calipers send digits in rapid succession (<80ms apart).
+     * Human typing is much slower (>100ms between keys).
+     */
+    _trackBurst() {
+      const now = performance.now();
+      const gap = now - this._lastKeyTime;
+
+      if (this._lastKeyTime > 0 && gap < 80) {
+        this._burstCount++;
+      } else {
+        this._burstCount = 1;
+      }
+
+      this._lastKeyTime = now;
     }
   };
 }