[MphoCodes]

The existing Android build had a non-executable Gradle 8 wrapper, an unconfigured shell runtime, duplicate alpha dependencies and stale manifest/resource entries. This establishes a reproducible Compose-ready build and CI while retaining the existing View screens and Firebase client configuration.

Task 1 only: AGP 9.3.3, Gradle 9.5.0, JDK 21, built-in Kotlin/Compose compiler 2.4.21, Java/Kotlin bytecode 17, compile SDK 37, minimum 27 and temporary target SDK 34. Target 36/system-bar/Back compatibility belongs to Task 2. Includes the exact version catalog, Firebase BOM/main-module import migration, official checksum-verified wrapper, debug-only Material 3 preview, host/API27 workflows and reproducible setup documentation. No opt-out flags, lint suppression/baseline, production Firebase change, later-stage features or merge.

Base: codex/android-modernization-spec at 0239eeb137303134e282be64071a8bde99942288; PR #1 was rechecked open/unmerged before push. This stacked PR contains only Task 1 changes.

Validation on JBR 21.0.10/macOS arm64:

• ./gradlew --no-daemon --stacktrace :app:checkDebugAarMetadata :app:assembleDebug :app:assembleDebugAndroidTest :app:lintDebug :app:testDebugUnitTest passed on the committed tree (87 tasks, 33s), including a compiled Compose function (JVM major 61 and generated Compose runtime parameters).
• The same five checks passed from a fresh tracked source export, with no IDE state, project cache/build output or local.properties (87 executed, 1m39s). Initial provisioning used an empty external SDK/cache; clean-source reproduction reused those external caches.
• Lint: 204 warnings, 0 errors. Existing resource/text/deprecation/update/temporary-target warnings remain visible; three native-alignment warnings identify the retained GIF 1.2.28 library. No errors were disabled.
• Unit XML report: 1 generated arithmetic test passed, 0 failures/errors/skips; build smoke evidence only.
• :app:connectedDebugAndroidTest -Pandroid.testInstrumentationRunnerArguments.class=com.example.acetimetracker.ExampleInstrumentedTest passed from the clean export: 1 test on a fresh API 27/Android 8.1 Google APIs ARM64 r3 AVD, emulator 37.2.12 build 16428233 (1m16s). Splash launched, Registration resumed, no AndroidRuntime fatal exception. No credentials entered or Firebase records changed.
• Wrapper ZIP and JAR matched official SHA-256 checksums; SDK CLI 23 installed platforms;android-37.0 revision 2 and AGP resolved compile SDK 37 successfully. The specified toolchain pins needed no adjustment.
• Fresh independent review: no Critical, Important or Minor findings after inspecting the full diff and actual host/clean/device evidence.
• Submitted-head GitHub Actions run 39234042052: success on 570b8dd0875f75a3985c4d0eb05470cfa0a116d5. Ubuntu 24.04/Temurin 21.0.12.1 host job passed all 87 acceptance tasks in 3m. The separate clean API27/default/x86_64 emulator job passed its one package test (emulator 37.2.12 build16428233; 74 tasks, 3m46s). Official SDK ZIP integrity checks passed in both jobs.

Plan rulings:

• Configuration and the compile-only preview use the real build checks; no artificial preview-text test, per the approved task.
• The plan's Gradle v5 and emulator runner v2 refs were annotated tag objects. The workflow uses their publisher-verified commit targets 0723195856401067f7a2779048b490ace7a47d7c and a421e43855164a8197daf9d8d40fe71c6996bb0d, preserving the selected families. Both actions resolved and completed successfully in the submitted-head workflow; an incorrect future pin would fail CI resolution.
• API27 Google APIs has no x86-64 package in the stable SDK inventory, so Linux CI uses the published default x86-64 image. The submitted-head device job installed and tested that image successfully; an incorrect future image choice would fail the independent device job.

The reviewer set aside Task2/later product behavior and release readiness under the approved Task1 scope. These remain unverified by this PR; target34 and retained native warnings make that boundary explicit. No deferred minor review findings.

Limitations: package/arithmetic tests do not cover auth, timer, migration or the later target-36 behavior. Retained native GIF 16KB alignment needs release-stage review. Setup commands and report locations: docs/development/android-setup.md.