feat(ci): publish PR Android APK to comment (#28283)

* feat(ci): publish PR Android APK to R2 with installable links

Adds a universal debug APK to PR builds and uploads it to a public
R2 bucket alongside the existing GitHub Actions artifact. Posts a
sticky PR comment with tap-to-install links and a QR code so testers
can install directly on their device without unzipping artifacts.

Required setup:
- Secrets: R2_APK_ACCESS_KEY_ID, R2_APK_SECRET_ACCESS_KEY,
  R2_APK_ACCOUNT_ID, R2_APK_BUCKET
- Optional repo variable: APK_PUBLIC_HOST (defaults to apk.immich.app)
- R2 bucket configured with a public custom domain matching APK_PUBLIC_HOST

* chore(ci): drop R2 upload, link directly to GitHub artifact

Surfaces the existing release-apk-signed artifact in a sticky PR
comment with a QR code. Avoids new infra and secrets — the trade-off
is GitHub login and a zip wrapper instead of tap-to-install.

* feat(ci): build PR APK as release and publish to GitHub Release

PR builds now produce a release APK signed with the release keystore.
The universal APK is published as a GitHub Release asset under tag
'pr-<num>' (prerelease), giving testers a direct, unzipped, tap-to-
install URL plus a QR code in the PR comment. The release-apk-signed
artifact is unchanged.

* chore(ci): drop GitHub Release, publish universal APK as own artifact

Reverts the prerelease publish. Uploads the universal release APK as
a separate single-file artifact so its download URL gives a zip
containing only that APK — no extra files to dig through. The QR in
the PR comment points at this universal-only artifact.

* chore(ci): build only universal APK for PR, drop split artifact

PR builds skip the arm64-only split — release-apk-signed now contains
just the universal app-release.apk, so the download zip is a single
file. Removes the redundant separate universal artifact and points
the PR comment QR at the main artifact URL.

* feat(mobile): suffix PR APK applicationId so it installs alongside production

Each PR build now becomes app.alextran.immich.pr<num> via PR_NUMBER env
read in build.gradle, so testers can install multiple PR builds and the
Play Store version on the same device without uninstalling. Also tags
the version with -pr<num> for visibility.

* feat(ci): allow PR APK build to run on forks

Forks can now run the Android build job. Steps that need repo secrets
(create-workflow-token, Create Keystore) are skipped when the PR is
from a fork, the checkout falls back to GITHUB_TOKEN, and build.gradle
falls back to debug signing if the release keystore isn't materialised.
The PR comment still requires write access, so it's gated to non-fork
PRs — fork APKs are reachable from the workflow run's artifact tab.

.github/workflows/build-mobile.yml

@@ -51,6 +51,7 @@ jobs:
       should_run: ${{ steps.check.outputs.should_run }}
     steps:
       - id: token
+        if: ${{ !github.event.pull_request.head.repo.fork }}
         uses: immich-app/devtools/actions/create-workflow-token@caa599d954228439ea3e8ce1c3328f41ab120ee6 # create-workflow-token-action-v2.0.0
         with:
           client-id: ${{ secrets.PUSH_O_MATIC_APP_CLIENT_ID }}
@@ -60,7 +61,7 @@ jobs:
         id: check
         uses: immich-app/devtools/actions/pre-job@91f342bb4477c4bc10c576ae739da875d85aa164 # pre-job-action-v2.0.4
         with:
-          github-token: ${{ steps.token.outputs.token }}
+          github-token: ${{ steps.token.outputs.token || github.token }}
           filters: |
             mobile:
               - 'mobile/**'
@@ -73,12 +74,13 @@ jobs:
     needs: pre-job
     permissions:
       contents: read
-    # Skip when PR from a fork
-    if: ${{ !github.event.pull_request.head.repo.fork && github.actor != 'dependabot[bot]' && fromJSON(needs.pre-job.outputs.should_run).mobile == true }}
+      pull-requests: write
+    if: ${{ github.actor != 'dependabot[bot]' && fromJSON(needs.pre-job.outputs.should_run).mobile == true }}
     runs-on: mich
 
     steps:
       - id: token
+        if: ${{ !github.event.pull_request.head.repo.fork }}
         uses: immich-app/devtools/actions/create-workflow-token@caa599d954228439ea3e8ce1c3328f41ab120ee6 # create-workflow-token-action-v2.0.0
         with:
           client-id: ${{ secrets.PUSH_O_MATIC_APP_CLIENT_ID }}
@@ -88,9 +90,10 @@ jobs:
         with:
           ref: ${{ inputs.ref || github.sha }}
           persist-credentials: false
-          token: ${{ steps.token.outputs.token }}
+          token: ${{ steps.token.outputs.token || github.token }}
 
       - name: Create the Keystore
+        if: ${{ !github.event.pull_request.head.repo.fork }}
         env:
           KEY_JKS: ${{ secrets.KEY_JKS }}
         working-directory: ./mobile
@@ -144,20 +147,40 @@ jobs:
           ANDROID_KEY_PASSWORD: ${{ secrets.ANDROID_KEY_PASSWORD }}
           ANDROID_STORE_PASSWORD: ${{ secrets.ANDROID_STORE_PASSWORD }}
           IS_MAIN: ${{ github.ref == 'refs/heads/main' }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
         run: |
           if [[ $IS_MAIN == 'true' ]]; then
             flutter build apk --release
             flutter build apk --release --split-per-abi --target-platform android-arm,android-arm64,android-x64
           else
-            flutter build apk --debug --split-per-abi --target-platform android-arm64
+            flutter build apk --release
           fi
 
       - name: Publish Android Artifact
+        id: upload-apk
         uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7.0.1
         with:
           name: release-apk-signed
           path: mobile/build/app/outputs/flutter-apk/*.apk
 
+      - name: Comment APK download link on PR
+        if: ${{ github.event_name == 'pull_request' && !github.event.pull_request.head.repo.fork }}
+        uses: mshick/add-pr-comment@8e4927817251f1ff60c001f04568532b38e0b4a0 # v3.11.0
+        env:
+          HEAD_SHA: ${{ github.event.pull_request.head.sha }}
+          APK_URL: ${{ steps.upload-apk.outputs.artifact-url }}
+        with:
+          github-token: ${{ steps.token.outputs.token }}
+          message-id: 'mobile-android-apk'
+          message: |
+            📱 **Android release APK (universal)** — `${{ env.HEAD_SHA }}`
+
+            Download: ${{ env.APK_URL }}
+
+            <img src="https://api.qrserver.com/v1/create-qr-code/?size=240x240&data=${{ env.APK_URL }}" alt="QR code" />
+
+            GitHub login required. Downloads as a zip containing a single `app-release.apk` — extract and install. Installs as a separate app (applicationId `app.alextran.immich.pr${{ github.event.pull_request.number }}`), so it coexists with the Play Store version and any other PR builds.
+
       - name: Save Gradle Cache
         id: cache-gradle-save
         uses: actions/cache/save@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5.0.5

mobile/android/app/build.gradle

@@ -64,8 +64,15 @@ android {
     }
 
     release {
-      signingConfig signingConfigs.release
+      def hasKeystore = file("../key.jks").exists() && file("../key.jks").length() > 0
+      signingConfig hasKeystore ? signingConfigs.release : signingConfigs.debug
       proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+
+      def prNumber = System.getenv("PR_NUMBER")
+      if (prNumber) {
+        applicationIdSuffix ".pr${prNumber}"
+        versionNameSuffix "-pr${prNumber}"
+      }
     }
   }
   namespace 'app.alextran.immich'