Paperless: poll consume task for real upload confirmation; v0.1.2

After POST /api/documents/post_document/ the client now polls /api/tasks/
until the document is consumed, so the app shows 'Toegevoegd ✓', 'Duplicaat',
or a failure message instead of just 'queued'. A 'Niet wachten' button lets
the user stop waiting (the POST itself is NonCancellable, so the document is
always really sent). Bump versionCode 3 / versionName 0.1.2.

Fixes #3

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/build.gradle.kts

@@ -24,8 +24,8 @@ android {
         applicationId = "eu.geyskens.pdfscan"
         minSdk = 26
         targetSdk = 35
-        versionCode = 2
-        versionName = "0.1.1"
+        versionCode = 3
+        versionName = "0.1.2"
 
         // OpenCV native libs are large; ship only the ABIs real phones use.
         ndk {