Fix vue assets under web base path (#711)

Remove hardcoded `--base=/app/` from npm build script and set `base:
'./'` in vite.config to generate relative asset URLs

Update server `updateBasePathInFrontend` to handle relative paths

Fixes #710

Signed-off-by: Rich C <richcarni@gmail.com>

frontend/package.json

@@ -3,8 +3,8 @@
   "version": "0.0.0",
   "scripts": {
     "dev": "vite",
-    "build-dev": "vite build --mode development --base=/app/",
-    "build": "vite build --base=/app/",
+    "build-dev": "vite build --mode development",
+    "build": "vite build",
     "preview": "vite preview --port 5050"
   },
   "dependencies": {

frontend/vite.config.mjs

@@ -5,6 +5,7 @@ import vue from '@vitejs/plugin-vue'
 
 // https://vitejs.dev/config/
 export default defineConfig({
+  base: './',
   plugins: [vue()],
   resolve: {
     alias: {