fix: allow HTTP to local instances in release build; fix activity 404 in dev

Android release builds block cleartext HTTP by default (debug builds override
this via the debug manifest overlay). Add usesCleartextTraffic=true to app.json
so expo prebuild includes it in the generated manifest — required to reach local
Bincio instances over HTTP.

In bincio dev (Astro dev server), /activity/<id>/ routes 404 because
getStaticPaths() returns [] and there is no nginx try_files fallback. Add a Vite
middleware plugin to astro.config.mjs that rewrites /activity/<id>/ to /activity/
in dev, matching what nginx does in production.

mobile/app.json

@@ -10,6 +10,7 @@
     "platforms": ["ios", "android"],
     "android": {
       "package": "org.bincio.app",
+      "usesCleartextTraffic": true,
       "permissions": [
         "android.permission.READ_EXTERNAL_STORAGE",
         "android.permission.READ_MEDIA_VIDEO",