Fix grammar and wording errors in i18n/en_US.yaml

Description

Several user-facing English strings in i18n/en_US.yaml contain spelling, grammar, word-form, or terminology errors.

The file is configured as the source locale in crowdin.yml, so these issues affect both the default English interface and the source text provided to translators.

I checked the current main branch and searched the existing issues and pull requests, but did not find an issue dedicated to this cleanup.

Steps to verify

1. Open i18n/en_US.yaml from the current main branch.
2. Locate the strings listed below.
3. Observe the spelling and grammatical errors in the displayed text.

Examples:

Answer do not found.
Comment are not allowed to edit.
Email verified URL has expired, please resend the email.
Recommend tag is not exist.
The from name cannot be a email address.
Email already existes.
Are you sure you wish to pinned globally?
Received a up vote.
Login failed, please allow this app to access your email information before try again.

Expected behavior

User-facing English text should use correct spelling, grammar, and consistent terminology.

For example:

Answer not found.
This comment cannot be edited.
The email verification URL has expired. Please resend the email.
Recommended tag does not exist.
The email sender name cannot be an email address.
Email already exists.
Are you sure you want to pin this post globally?
Received an upvote.
Login failed. Please allow this app to access your email information before trying again.

Proposed changes

Correct the affected English copy in i18n/en_US.yaml, including:

• backend error messages;
• moderation reason descriptions;
• badge descriptions;
• form validation messages;
• other user-facing UI messages.

The proposed cleanup currently covers 43 strings.

The change will not:

• rename, add, or remove translation keys;
• change interpolation placeholders;
• modify application behavior;
• directly modify translated locale files.

Validation

The updated file will be checked to ensure that:

• it remains valid YAML;
• no translation keys are added or removed;
• all interpolation placeholders are preserved.

I would like to work on this and submit a pull request.