Update ag2 version to 0.8.4 and add support for new version

[kumaranvpl]

Description

Fixes #653

Type of change

• Documentation (typos, code examples, or any documentation updates)
• Bug fix (a non-breaking change that resolves an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a fix or feature that would disrupt existing functionality)
• This change requires a documentation update

Checklist

• I have conducted a self-review of my own code
• I have made the necessary changes to the documentation
• My changes do not generate any new warnings
• I have added tests to validate the effectiveness of my fix or the functionality of my new feature
• I have included code examples to illustrate the modifications

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files with missing lines	Coverage Δ
fastagency/runtimes/ag2/agents/websurfer.py	100.00% <ø> (ø)
fastagency/runtimes/ag2/agents/whatsapp.py	50.00% <ø> (ø)
fastagency/runtimes/ag2/tools/websurfer.py	82.85% <ø> (ø)

... and 1 file with indirect coverage changes

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[Copilot]

Pull Request Overview

This PR upgrades the ag2 dependency from version 0.8.1 to 0.8.4 and updates test and agent type annotations to use LLMConfig instead of dicts.

• Upgrade ag2 dependency and update version strings.
• Replace type hints for LLM configurations in tests, agents, and tools from dict[str, Any] to LLMConfig.
• Adjust error handling in test cases to align with pydantic ValidationError messages.

Reviewed Changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/runtime/ag2/tools/test_whatsapp.py	Updated type hints for LLM config in test functions.
tests/runtime/ag2/tools/test_web_surfer.py	Updated type hints and error exception from ValueError to ValidationError.
tests/runtime/ag2/test_autogen.py	Modified function signatures to use LLMConfig.
tests/conftest.py	Changed fixture return types to LLMConfig and modified azure_model_llm_config accordingly.
tests/api/openapi/*	Updated type hints for LLM config in various API endpoint tests.
pyproject.toml	Upgraded the ag2 dependency version.
fastagency/runtimes/ag2/*	Updated type hints for LLM configurations in tools and agents.
fastagency/about.py	Updated package version to 0.8.4.

Comments suppressed due to low confidence (1)

tests/runtime/ag2/tools/test_web_surfer.py:24

• The test now expects a 'ValidationError' with match 'Field required'. However, pydantic's error messages can include additional detail. Consider using a more flexible regex (e.g. ".required.") to avoid brittle tests if the message format changes slightly.

ValidationError,