chores: fix smithy/config-resolver dependabot alert

[sarayev]

Description of changes:

Resolves Dependabot security alert for @smithy/config-resolver (CVE CVSS 3.7 LOW - region validation vulnerability).

Changes:

• Upgraded aws-amplify from ^6.0.9 to ^6.15.9 to get latest security updates
• Added resolution for @smithy/config-resolver to ^4.4.5 to ensure all transitive dependencies use the patched version
• All @smithy/config-resolver versions now >= 4.4.6 (safe)

Testing:

• All 195 unit tests passing
• Linter checks passing
• No security vulnerabilities remaining for @smithy/config-resolver

This follows the same approach used in aws-amplify/amplify-ui PR #6801.

Related GitHub issue #, if available:

Fixes Dependabot security alert #117

Instructions

If this PR should not be merged upon approval for any reason, please submit as a DRAFT

Which product(s) are affected by this PR (if applicable)?

• amplify-cli
• amplify-ui
• amplify-studio
• amplify-hosting
• amplify-libraries

Which platform(s) are affected by this PR (if applicable)?

• JS
• Swift
• Android
• Flutter
• React Native

Please add the product(s)/platform(s) affected to the PR title

Checks

• Does this PR conform to the styleguide?
• Does this PR include filetypes other than markdown or images? Please add or update unit tests accordingly.
• Are any files being deleted with this PR? If so, have the needed redirects been created?
• Are all links in MDX files using the MDX link syntax rather than HTML link syntax?
  ref: MDX: [link](https://docs.amplify.aws/) HTML: <a href="https://docs.amplify.aws/">link</a>

When this PR is ready to merge, please check the box below

• Ready to merge

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.