fix(formulus): align Android release packaging and version codes

[r0ssing]

Align Android release packaging and version codes

Acknowledgements

Many thanks and ❤️ to @licaon-kter for identifying and clearly explaining the F-Droid version-code collision in #746.

We also greatly appreciate the ongoing work of the F-Droid maintainers and contributors. Their review, packaging, and reproducible-build efforts help make Formulus available through a trusted FOSS distribution channel.

Summary

Fix the Formulus Android release packaging and version-code strategy following the transition from ABI-specific GitHub APKs to a single universal APK.

This PR:

• Moves the Android release versionCode from 36 to 40.
• Aligns both iOS CURRENT_PROJECT_VERSION values to 40.
• Introduces a four-code release block policy: 40, 44, 48, etc.
• Limits normal GitHub and Google Play builds to physical ARM devices:
  • armeabi-v7a
  • arm64-v8a
• Keeps F-Droid's four independent ABI builds, including x86 and x86_64.
• Adds CI validation for native version and build-number alignment.
• Updates the Android release and CI/CD documentation.

Closes #746.

Background

Version-code collision

The previous ABI-specific APK setup assigned consecutive version codes to different ABIs. For example, a base code of 36 could produce GitHub APKs with codes 36–39.

F-Droid similarly derives four codes from the upstream source code:

ABI	Derived code with base 40
armeabi-v7a	40
arm64-v8a	41
x86	42
x86_64	43

After switching the GitHub artifact to a universal APK, the universal build used the unmodified base code 36. Android therefore treated it as a downgrade on devices with an ABI-specific APK using code 37, 38, or 39.

Base 40 is the first code above:

• The F-Droid 1.3.0 block (35–38).
• The old GitHub 1.3.1 split range (36–39).

APK size

The four-ABI universal APK included native libraries for ARM32, ARM64, x86, and x86_64, increasing its size from approximately 36 MB to 85 MB.

Normal GitHub and Play builds now target only:

• armeabi-v7a
• arm64-v8a

This retains coverage for 32-bit and 64-bit physical Android devices without carrying emulator-focused x86 libraries in every direct download.

F-Droid remains able to build all four ABIs because its metadata explicitly invokes Gradle with -PabiFilters=<abi>, bypassing the normal ARM-universal configuration.

Version-code policy

Going forward, each distinct APK/AAB shipped on a GitHub Release or uploaded to Play should use the next four-code-aligned base:

40, 44, 48, 52, ...
The base is used by:

- GitHub universal APK
- Google Play AAB
- iOS `CURRENT_PROJECT_VERSION`

F-Droid reserves the full block from `base` through `base + 3`.

Ordinary branch CI artifacts do not consume a new block.

Before a release, the selected base must also be checked against the highest code already uploaded to Google Play.

## CI safeguards

Adds:

```bash
pnpm run validate:native-versions

The validator checks that:

• Android versionCode is divisible by four.
• Android versionName matches formulus/package.json.
• Both iOS CURRENT_PROJECT_VERSION values match Android.
• iOS MARKETING_VERSION matches formulus/package.json.

The Android workflow runs this validation before building.

Validation

• pnpm run validate:native-versions
• Prettier checks for changed Formulus files
• ESLint for the native-version validator
• git diff --check
• Workflow and Gradle editor diagnostics
• Gradle configuration with normal ARM32/ARM64 settings
• Gradle configuration with F-Droid-style -PabiFilters=x86

A complete signed APK/AAB build was not run locally; CI will build and report the resulting artifact sizes.