v1.2.0 — Multi-piece, NMFC lookup, PDF export, defaults, CSV history, density gauge + bug fixes

Features added:
- Multi-piece support: add unlimited pieces each with L x W x H x Weight, combined class from total density
- NMFC commodity lookup: 55 bundled items, live search by name or code
- PDF export: branded PDF with piece table, Cu Ft, PCF, freight class via jsPDF
- Default piece preset: save a standard pallet size in Settings > Defaults
- Export/import history as CSV
- Density gauge: color gradient bar with live marker in results panel
- Unit toggle: in/cm and lbs/kg with live conversion across all pieces
- Copy to clipboard, timestamps in history, Enter key shortcut, input validation
- Charcoal dark mode

Bug fixes:
- PDF and Copy now blocked before a calculation is performed
- History restore no longer misconverts values when units differ from stored unit
- History display shows correct unit labels (cm/kg) instead of hardcoded in/lbs
- PDF logo format auto-detected from data URL (fixes silent failure for JPG uploads)
- Removed dead parsedPieces variable; forEach with early return prevents NaN accumulation
- Removed no-op placeholder update in applyUnitToggleUI
- CSV export URL revocation deferred to avoid race condition

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

package.json

@@ -5,7 +5,8 @@
   "main": "main.js",
   "scripts": {
     "start": "electron .",
-    "build": "electron-builder --win"
+    "build": "electron-builder --win",
+    "serve": "node server.js"
   },
   "author": "",
   "license": "ISC",

server.js

@@ -0,0 +1,34 @@
+const http = require('http');
+const fs = require('fs');
+const path = require('path');
+
+const PORT = 3010;
+
+const mimeTypes = {
+    '.html': 'text/html',
+    '.js':   'application/javascript',
+    '.css':  'text/css',
+    '.png':  'image/png',
+    '.ico':  'image/x-icon',
+    '.json': 'application/json',
+};
+
+const server = http.createServer((req, res) => {
+    const filePath = path.join(__dirname, req.url === '/' ? 'index.html' : req.url);
+    const ext = path.extname(filePath);
+    const contentType = mimeTypes[ext] || 'application/octet-stream';
+
+    fs.readFile(filePath, (err, data) => {
+        if (err) {
+            res.writeHead(404, { 'Content-Type': 'text/plain' });
+            res.end('404 Not Found');
+            return;
+        }
+        res.writeHead(200, { 'Content-Type': contentType });
+        res.end(data);
+    });
+});
+
+server.listen(PORT, () => {
+    console.log(`Freight Calculator Pro running at http://localhost:${PORT}`);
+});