BUG: Unchecked io.ReadAll() errors in fetcher.go

[andrinoff]

Describe the bug
Multiple calls to ioutil.ReadAll() in fetcher/fetcher.go ignore returned errors, potentially leading to silent data loss or partial reads.

To reproduce

1. Examine fetcher/fetcher.go line 137 in decodePart() function
2. Examine fetcher/fetcher.go line 740 in attachment parsing
3. Notice errors from ReadAll() are assigned to _ and ignored

Code locations:

Line 137:

body, _ := ioutil.ReadAll(reader)  // Error ignored
return string(body), nil

Line 740:

b, _ := ioutil.ReadAll(p.Body)  // Error ignored

Expected behavior
Errors from ReadAll() should be checked and propagated. If reading fails, function should return error rather than empty/partial data.

Additional context

• This is good first issue - straightforward error handling fix
• Side benefit: replace deprecated ioutil.ReadAll() with io.ReadAll() (deprecated since Go 1.16)
• Similar pattern exists in multiple locations

Suggested fix:

body, err := io.ReadAll(reader)
if err != nil {
    return "", fmt.Errorf("failed to read body: %w", err)
}
return string(body), nil