Add GitHub configuration: CI/CD, templates, and dependabot

[IISweetHeartII]

Problem Statement

The repository lacks CI/CD workflows, issue/PR templates, and dependency management configuration.

Proposed Solution

Add complete .github/ directory with:

• CI workflow (test, lint, type-check on Python 3.9-3.12)
• Auto-release workflow (tag + publish to PyPI on main merge)
• Auto-label workflow (label PRs by file path + size)
• Issue templates (bug report, feature request)
• PR template
• Dependabot config (pip + github-actions)
• Release changelog configuration

Checklist

• CI workflow (.github/workflows/ci.yml)
• Auto-release workflow (.github/workflows/auto-release.yml)
• Auto-label workflow (.github/workflows/auto-label.yml)
• Labeler config (.github/labeler.yml)
• Dependabot config (.github/dependabot.yml)
• Bug report template (.github/ISSUE_TEMPLATE/bug_report.yml)
• Feature request template (.github/ISSUE_TEMPLATE/feature_request.yml)
• Issue template config (.github/ISSUE_TEMPLATE/config.yml)
• PR template (.github/PULL_REQUEST_TEMPLATE.md)
• Release config (.github/release.yml)