refactor: migrate deploy-android-bundle to Dagger (#449)

## Summary

- Deletes `scripts/build_android_bundle_local.sh`, which required a host Android SDK and failed with `No Android SDK found`
- Removes the `build-android-bundle-local` Taskfile task that invoked it
- Rewrites `deploy-android-bundle` to call the existing Dagger `publish-android` pipeline (build → stamp versionCode → sign → upload) via `sops exec-env` for local secret injection — no local Android SDK needed

The `publish-android` Dagger function (`ci/main.go`) already handles everything the old script did (keystore decode, AAB build, signing) plus version-code stamping, so no changes to `ci/main.go` are required.

Closes #444

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Co-authored-by: Thomas SharedInbox <sharedinbox@thomas-guettler.de>
Reviewed-on: https://codeberg.org/guettli/sharedinbox/pulls/449

scripts/build_android_bundle_local.sh

@@ -1,15 +0,0 @@
-#!/usr/bin/env bash
-set -euo pipefail
-
-tmp=$(mktemp /dev/shm/keystore.XXXXXX.jks)
-trap "rm -f $tmp" EXIT
-
-printf '%s' "$ANDROID_KEYSTORE_BASE64" | base64 -d > "$tmp"
-
-ANDROID_KEYSTORE_PATH="$tmp" \
-ANDROID_HOME="${ANDROID_HOME:-$HOME/Android/Sdk}" \
-fvm flutter build appbundle --release --no-pub \
-  --build-number "$(date +%s)" \
-  --build-name "$(date +%y%m%d-%H%M)" \
-  --dart-define="GIT_HASH=$(git rev-parse --short HEAD)" \
-  | grep -Ev "was tree-shaken|Tree-shaking can be disabled"