Prepare 0.82.1 release

[FeodorFitsner]

Summary

Prepare 0.82.1 release artifacts:

• bump packages/flet version to 0.82.1
• refresh client/pubspec.lock
• add 0.82.1 entries to root and package changelogs
• convert flet-ads changelog Unreleased section to 0.82.1
• switch changelog author attributions to linked GitHub profiles
• update release skill guidance to require linked author attribution format

Notes

• release notes are based on changes since v0.82.0
• branch 0.82.1 existence was verified for both template repos during prep

Summary by Sourcery

Prepare the 0.82.1 patch release including version bumps, changelog updates, and release process guidance tweaks.

Bug Fixes:

• Document and ship fixes for lazy-loading optional auth dependencies to prevent web/Pyodide import-time failures.
• Document and ship a dependency pin for binaryornot < 0.5 to resolve build-template UTF-8 decode errors.

Enhancements:

• Finalize the flet-ads package 0.82.1 changelog entry, promoting previous unreleased improvements to a tagged release.
• Refine the release preparation skill to require linked GitHub profile attributions, ensure milestones are applied, and include branch creation from main in the workflow.

Build:

• Bump the packages/flet package version to 0.82.1 and refresh the client pubspec.lock to align with the new release.

[sourcery-ai]

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