Improve user-friendly error output for Fluent

[m-xim]

FTL file:

hello = Hello, <b>{ $firstname } { $lastname }</b>!

Before:

fluent.runtime.errors.FluentReferenceError: Unknown external: firstname

After:

aiogram_i18n.exceptions.FluentMessageError: 
2 errors for key 'hello':
  Unknown external: firstname (type=FluentReferenceError)
  Unsupported external type: lastname, <class 'NoneType'> (type=TypeError)

[m-xim]

@andrew000

[Copilot]

Pull Request Overview

This PR improves error handling for Fluent translation errors by introducing a new FluentMessageError exception that aggregates multiple errors and formats them in a user-friendly way. Instead of only raising the first error encountered during Fluent message formatting, all errors are now collected and presented together with their types.

• Introduces FluentMessageError exception for better error reporting
• Updates both Fluent runtime and compile cores to use the new exception
• Fixes duplicate function names in example code

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/aiogram_i18n/exceptions.py	Adds new FluentMessageError exception class with formatted multi-error output
src/aiogram_i18n/cores/fluent_runtime_core.py	Updates error handling to raise FluentMessageError instead of first error only
src/aiogram_i18n/cores/fluent_compile_core.py	Updates error handling to raise FluentMessageError instead of first error only
examples/language_inline_markup.py	Renames duplicate function names from btn_help to btn_back and btn_lang

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[Copilot]

Pull Request Overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

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_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[Copilot]

Pull Request Overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

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_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}