feat(android): use FlutterFragmentActivity and AppCompat LaunchTheme for biometrics

[mccre110]

Description

Android host infrastructure required for biometric authentication and other plugins that need a FragmentActivity (e.g. local_auth).

Changes:

• FlutterActivity → FlutterFragmentActivity in the dev client and flet build template
• LaunchTheme parent → Theme.AppCompat.DayNight.NoActionBar (light + night) so biometric dialogs work on API 24–27
• biometric cross-platform permission bundle (NSFaceIDUsageDescription for iOS/macOS)
• Face ID usage string in dev client Info.plist
• macOS publish docs: Touch ID signing notes; fixed service doc links
• Changelog entry under ## Unreleased → Improvements

This PR is intentionally separate from the flet-local-auth extension so the host-app blast radius can be reviewed and reverted independently. The extension PR stacks on this one.

Related: closes #3192 (supersedes closed #3682) and #5226.

Note: FlutterFragmentActivity R8 keep-rule docs in website/docs/publish/android.md depend on the ProGuard/R8 docs section landing on release/flet-1.0 (on main via #6741). Functional code does not depend on that docs section.

Test code

# No Python API in this PR — verify Android template builds and biometric permission bundle:

# flet build apk / aab with:
# [tool.flet]
# permissions = ["biometric"]

# Confirm generated Android project uses FlutterFragmentActivity and AppCompat LaunchTheme.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist

• I signed the CLA.
• I have performed a self-review of my own code.
• My code follows the style guidelines of this project.
• I have commented my code, particularly in hard-to-understand areas.
• My changes generate no new warnings.
• New and existing tests pass locally with my changes.
• I have made corresponding documentation changes, if applicable.
• I have added changelog entries for user-facing changes, if applicable.
• I have updated release guide pages and website/sidebars.yml for breaking changes, removals, and deprecations, if applicable.

Screenshots

N/A — host/template change; no UI change beyond correct biometric dialog behavior on Android.

Additional details

N/A

Summary by Sourcery

Update Android host apps and templates to support biometric authentication and add a cross-platform biometric permission bundle with accompanying documentation and changelog entry.

New Features:

• Introduce a biometric cross-platform permission bundle that injects Face ID usage descriptions for iOS and macOS builds.

Enhancements:

• Switch Android dev client and template main activities to FlutterFragmentActivity to support plugins requiring a FragmentActivity, such as biometric authentication.
• Adopt an AppCompat LaunchTheme (Theme.AppCompat.DayNight.NoActionBar) for Android launch screens in the dev client and templates to ensure biometric dialogs work correctly on older API levels.

Documentation:

• Document the biometric permission bundle behavior for macOS, including how to override Face ID usage descriptions.
• Add an unreleased changelog entry describing the Android host and biometric permission changes.

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Hey - I've reviewed your changes and they look great!

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[FeodorFitsner]

The PR looks like a "base" for another one?

[mccre110]

The PR looks like a "base" for another one?

Yes for #6759. I wanted to create separate branches, but permissions were an issue. We can close this first then by #6759. The other PR includes all the changes together, so we can decide on the best merge method.

[FeodorFitsner]

Got it. Let's close this PR and review #6759 then.