Bump version to 1.3.0 and exclude tauri/ from Electron build

The Electron build was accidentally bundling the entire tauri/src-tauri/target
Rust build directory into app.asar (1.2GB!), inflating the installer to 304MB.
Added a files exclusion so Electron and Tauri builds stay independent.

tauri/src-tauri/tauri.conf.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
   "productName": "Freight Calculator Pro",
-  "version": "1.2.0",
+  "version": "1.3.0",
   "identifier": "com.freightcalc.pro",
   "build": {
     "frontendDist": "../dist"