Enable full PWA install experience in all web modes

- Add PWAInstallPrompt component for custom install UI and event handling
- Register PWAInstallPrompt in App.vue for global visibility
- Enable PWA features and install prompt in dev, test, and prod (vite.config.web.mts)
- Update service worker registration to work in all environments
- Update docs/build-web-script-integration.md with PWA install guidance and visual cues
- Add scripts/build-web.sh for unified web build/dev workflow

PWA is now installable and testable in all web environments, with clear user prompts and desktop support.

src/registerServiceWorker.ts

@@ -2,13 +2,9 @@
 
 import { register } from "register-service-worker";
 
-// Only register service worker if:
-// 1. PWA is explicitly enabled
-// 2. In production mode
-if (
-  process.env.VITE_PWA_ENABLED === "true" &&
-  process.env.NODE_ENV === "production"
-) {
+// Register service worker if PWA is enabled
+// Enable in all environments for consistent testing and functionality
+if (process.env.VITE_PWA_ENABLED === "true") {
   register(`${process.env.BASE_URL}sw.js`, {
     ready() {
       console.log("Service worker is active.");
@@ -36,10 +32,6 @@ if (
   });
 } else {
   console.log(
-    `Service worker registration skipped - ${
-      process.env.VITE_PWA_ENABLED !== "true"
-        ? "PWA not enabled"
-        : "not in production mode"
-    }`,
+    `Service worker registration skipped - PWA not enabled (VITE_PWA_ENABLED=${process.env.VITE_PWA_ENABLED})`,
   );
 }