Improve app UX (server setup, status, gallery, log) and allow

manual CI publishes

- Settings: prefill an editable example server URL, add a "Test
  connection" button
- Front page now shows the receipts list (Overview) with a column
  header and an empty-state message
- Add a connection status bar (polls /health) shown on every screen
- Capture: add "Choose from gallery" alongside the camera
- Add an in-app "App log" screen; ApiClient/CaptureViewModel/
  OverviewViewModel/ConnectionStatusViewModel now log key events,
  including the actual connection-failure reason (not just pass/fail)
- .gitea/workflows/build.yml: publish to dl.ladkau.de on a manual
  "Run workflow" dispatch too, not just push
- README.md: document the CI secrets (REGISTRY_USER/PASSWORD,
  DL_SFTP_KEY) that must be configured in Gitea, separate from the
  local registry.env

.gitea/workflows/build.yml

@@ -57,9 +57,11 @@ jobs:
 
       - name: Publish to dl.ladkau.de
         # Uploads the APK over SFTP instead of using actions/upload-artifact
-        # (whose zip wrapping can't be disabled). Only runs on push so PR
-        # builds don't publish.
-        if: gitea.event_name == 'push'
+        # (whose zip wrapping can't be disabled). Runs on push and on a
+        # manual "Run workflow" dispatch (the on-demand way to publish an
+        # update without pushing a commit) - excludes pull_request so PR
+        # builds from unreviewed branches don't publish.
+        if: gitea.event_name == 'push' || gitea.event_name == 'workflow_dispatch'
         run: |
           set -euo pipefail
           APK="$(ls dist/fuelish-*.apk)"