feat: add flet-local-auth extension

[mccre110]

Description

Adds the flet-local-auth extension with a LocalAuthentication service for on-device biometric and credential authentication on Android, iOS, macOS, and Windows via local_auth 3.0.2. Linux and Web are explicitly unsupported.

Stacks on: the Android host PR (FlutterFragmentActivity + AppCompat LaunchTheme). Merge that PR first.

API:

• is_device_supported(), can_check_biometrics(), get_available_biometrics()
• authenticate() — raises LocalAuthException on failure (upstream local_auth parity)
• stop_authentication()
• Platform auth message types (AndroidAuthMessages, IOSAuthMessages, etc.) aligned with local_auth 3.x

Includes Python package, Flutter extension, client registration, CI, docs, example, and integration tests.

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

Test code

import flet as ft
import flet_local_auth as auth


async def main(page: ft.Page):
  local_auth = auth.LocalAuthentication()
  print(await local_auth.is_device_supported())
  print(await local_auth.can_check_biometrics())
  print(await local_auth.get_available_biometrics())
  try:
    ok = await local_auth.authenticate("Unlock to continue")
    print("authenticated:", ok)
  except auth.LocalAuthException as e:
    print("failed:", e.code)


ft.run(main)

Integration tests: sdk/python/packages/flet/integration_tests/extensions/local_auth/test_local_auth.py

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

Service invokes the OS biometric modal; no custom Flet UI.

Additional details

N/A

Summary by Sourcery

Add a new cross-platform local authentication service and extension, wiring it into the client, build tooling, and documentation so apps can use on-device biometrics and credentials on supported platforms.

New Features:

• Introduce the flet-local-auth Python package and Flutter extension exposing a LocalAuthentication service with methods for capability checks and user authentication on Android, iOS, macOS, and Windows.
• Provide an example app and gallery metadata demonstrating how to use LocalAuthentication and customize platform-specific auth messages.

Enhancements:

• Register the local_auth plugins on Windows and macOS, and enable the flet-local-auth extension in the client so authentication works across desktop and mobile targets.
• Switch Android host activities and app templates to FlutterFragmentActivity with an AppCompat LaunchTheme to support biometric dialogs and modern theming.
• Add a biometric cross-platform permission bundle and NSFaceIDUsageDescription defaults for iOS and macOS builds.
• Wire flet-local-auth into the workspace, tooling, and build/test configs, including dependency lists and crocodocs sources.

Documentation:

• Add user-facing documentation pages for the LocalAuthentication service and its related types, and link them into the docs sidebar and built-in extensions list.
• Extend macOS publishing docs with guidance on Touch ID/Face ID usage, signing requirements, and keychain considerations for local authentication.

Tests:

• Add Flutter unit tests for enum/error-code mapping in the local auth utility and Python integration tests validating platform support and device capability APIs for LocalAuthentication.

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[sourcery-ai]

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