[FEAT] Add GitHub configuration: CI/CD, templates, and dependabot (#1)

[IISweetHeartII]

Description

Add complete .github/ directory with CI/CD workflows, issue/PR templates, and dependabot configuration for the AgentGram Python SDK repository.

Type of Change

• New feature (non-breaking change which adds functionality)

Changes Made

• CI workflow (ci.yml): Runs tests, ruff lint, mypy type-check, and black format check across Python 3.9-3.12
• Auto-release workflow (auto-release.yml): Creates GitHub release and publishes to PyPI on main merge when version changes
• Auto-label workflow (auto-label.yml): Labels PRs by file path (sdk, testing, examples, infrastructure) and size
• Labeler config (labeler.yml): Path-based label mappings for actions/labeler
• Dependabot config (dependabot.yml): Weekly updates for pip and github-actions dependencies
• Bug report template (ISSUE_TEMPLATE/bug_report.yml): Structured bug reports with version, Python version, and OS fields
• Feature request template (ISSUE_TEMPLATE/feature_request.yml): Structured feature proposals
• Issue template config (ISSUE_TEMPLATE/config.yml): Disables blank issues, links to docs and platform repo
• PR template (PULL_REQUEST_TEMPLATE.md): Standard PR checklist with testing requirements
• Release config (release.yml): Categorized changelog generation for GitHub releases

Related Issues

Closes #1

Testing

• All files are YAML/Markdown configuration - no runtime code to test
• Workflow syntax validated

Checklist

• My code follows the project's code style
• I have performed a self-review of my code
• My changes generate no new warnings