replace: swap prosappweb content for prosapp_web_app (more complete version)

prosapp_web_app has chat, dashboard, calendar, support, 13 providers and
Fluro URL routing. Keep Dockerfile + nginx.conf from previous prosappweb.
Upgrade google_fonts 6.2.1 → 8.1.0 (Dart 3.12 compat fix).

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

lib/utils/constants.dart

@@ -0,0 +1 @@
+const String API_BASE_URL = String.fromEnvironment('API_BASE_URL', defaultValue: 'http://localhost:3000/api/v1');