[auth] Add workflow for internal release (#3259)

## Description

## Tests

.github/workflows/auth-internal-release.yml

@@ -0,0 +1,56 @@
+name: "Internal release (auth mobile)"
+
+on:
+    workflow_dispatch: # Allow manually running the action
+
+env:
+    FLUTTER_VERSION: "3.24.1"
+
+jobs:
+    build:
+        runs-on: ubuntu-latest
+
+        defaults:
+            run:
+                working-directory: auth
+
+        steps:
+            - name: Checkout code and submodules
+              uses: actions/checkout@v4
+              with:
+                  submodules: recursive
+
+            - name: Setup JDK 17
+              uses: actions/setup-java@v1
+              with:
+                  java-version: 17
+
+            - name: Install Flutter ${{ env.FLUTTER_VERSION  }}
+              uses: subosito/flutter-action@v2
+              with:
+                  channel: "stable"
+                  flutter-version: ${{ env.FLUTTER_VERSION  }}
+                  cache: true
+
+            - name: Setup keys
+              uses: timheuer/base64-to-file@v1
+              with:
+                  fileName: "keystore/ente_auth_key.jks"
+                  encodedString: ${{ secrets.SIGNING_KEY_PHOTOS }}
+
+            - name: Build PlayStore AAB
+              run: |
+                  flutter build appbundle --release --flavor playstore --dart-define=app.flavor=playstore
+              env:
+                  SIGNING_KEY_PATH: "/home/runner/work/_temp/keystore/ente_auth_key.jks"
+                  SIGNING_KEY_ALIAS: ${{ secrets.SIGNING_KEY_ALIAS }}
+                  SIGNING_KEY_PASSWORD: ${{ secrets.SIGNING_KEY_PASSWORD }}
+                  SIGNING_STORE_PASSWORD: ${{ secrets.SIGNING_STORE_PASSWORD }}
+
+            - name: Upload AAB to PlayStore
+              uses: r0adkll/upload-google-play@v1
+              with:
+                  serviceAccountJsonPlainText: ${{ secrets.SERVICE_ACCOUNT_JSON }}
+                  packageName: io.ente.auth
+                  releaseFiles: auth/build/app/outputs/bundle/playstoreRelease/app-playstore-release.aab
+                  track: internal