feat(useraccount): user name and avatar can be updated

[pan93412]

No description provided.

[linear]

DBP-87 實作 user 預先註冊

[Copilot]

Pull Request Overview

This PR enables automatic updates of user names and avatars when existing users authenticate through OAuth providers. Previously, when an existing user logged in, their name and avatar would remain unchanged from the original values.

• Updates existing user name and avatar fields to match OAuth provider information during login
• Adds comprehensive test coverage for various scenarios including verified users and empty avatar handling
• Modifies test assertions to verify the new update behavior instead of preserving original values

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
internal/useraccount/register_flow.go	Adds logic to update existing user's name and avatar with OAuth data
internal/useraccount/register_flow_test.go	Adds test cases for name/avatar updates and updates existing test assertions

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