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:

```text
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:

```text
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.

Öffne i18n/en_US.yaml aus dem aktuellen main-Branch und überprüfe die 43 aufgeführten nutzerseitig sichtbaren Zeichenfolgen. Verwende crowdin.yml, um zu bestätigen, dass es sich um das Quellgebietsschema handelt. Bewahre jeden Übersetzungsschlüssel und jeden Interpolationsplatzhalter und korrigiere dabei die Formulierung. Validiere, dass die Datei gültiges YAML bleibt und dass Schlüssel und Platzhalter unverändert sind.

Vom Indexierungsmodell aus dem Issue-Text verfasst.