feat: add PR size labeler workflow

[lukas-kuntze]

Description

Add GitHub Actions workflow to automatically label pull requests based on their size using devx-action-pr-size-labeler.

• Triggers on PR open, reopen, and synchronize events
• Uses custom size configuration from .github/config/size-labels.yml

Fixes # N/A

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Type of Change

Please select the applicable option(s):

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that breaks existing functionality)
• This change requires a documentation update

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How Has This Been Tested?

• Manual testing with label configuration file
• Verified label creation, update, and deletion operations
• Tested with different configuration sources (local file, URL)

Test Configuration:

• Node version: 20.x
• Operating system: Ubuntu (GitHub Actions runner)

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Checklist

• No secrets (e.g., passwords, tokens, API keys) are included in plain text in this pull request
• The pull request title is formatted as: [ISSUE-XXXX] – Short description or <type>: Short description, where ISSUE-XXXX is replaced with the corresponding ticket number from the issue tracker.
  Best practice: Use the issue title in the PR title and in the first line of the commit message.
• Code follows the project conventions
• Self-review of the code has been performed
• Relevant documentation has been updated
• New and existing tests pass successfully
• The pull request is labeled with at least one of the known labels for release notes:
  • feat / feature: New features or enhancements (minor version)
  • fix: Bug fix (patch version)
  • docs: Documentation added/changed
  • style: Changes without impact on functionality (formatting, whitespace, etc.)
  • refactor: Code restructuring without bug fix or new feature
  • perf: Performance improvement
  • test: Adding/correcting tests
  • build: Changes to build system or dependencies
  • ci: Changes to CI configuration/scripts
  • chore: Other changes
  • revert: Revert a change

Note: If your branch was created with one of these prefixes, the label will be set automatically.
Example: If the source branch is feat/<branch-name>, the PR will automatically receive the feature label.